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11 pages, 1829 KiB

Open AccessArticle

Reactive Pad-Steam Dyeing of Cotton Fabric Modified with Cationic P(St-BA-VBT) Nanospheres

by Kuanjun Fang, Dawu Shu, Xiuming Liu, Yuqing Cai, Fangfang An and Xinqing Zhang

Polymers 2018, 10(6), 564; https://doi.org/10.3390/polym10060564 - 23 May 2018

Cited by 25 | Viewed by 6199

Abstract

The Poly[Styrene-Butyl acrylate-(P-vinylbenzyl trimethyl ammonium chloride)] P(St-BA-VBT) nanospheres with N⁺(CH₃)₃ functional groups were successfully prepared and applied to modify cotton fabrics using a pad-dry process. The obtained cationic cotton fabrics were dyed with pad-steam dyeing with reactive dye. [...] Read more.

The Poly[Styrene-Butyl acrylate-(P-vinylbenzyl trimethyl ammonium chloride)] P(St-BA-VBT) nanospheres with N⁺(CH₃)₃ functional groups were successfully prepared and applied to modify cotton fabrics using a pad-dry process. The obtained cationic cotton fabrics were dyed with pad-steam dyeing with reactive dye. The results show that the appropriate concentration of nanospheres was 4 g/L. The sodium carbonate of 25 g/L and steaming time of 3 min were suitable for dyeing cationic cotton with 25 g/L of C.I. Reactive Blue 222. The color strength and dye fixation rates of dyed cationic cotton fabrics increased by 39.4% and 14.3% compared with untreated fabrics. Moreover, sodium carbonate and steaming time were reduced by 37.5% and 40%, respectively. The rubbing and washing fastness of dyed fabrics were equal or higher 3 and 4–5 grades, respectively. Scanning electron microscopy (SEM) images revealed that the P(St-BA-VBT) nanospheres randomly distributed and did not form a continuous film on the cationic cotton fiber surfaces. The X-ray photoelectron spectroscopy (XPS) analysis further demonstrated the presence of cationic nanospheres on the fiber surfaces. The cationic modification did not affect the breaking strength of cotton fabrics. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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17 pages, 3207 KiB

Open AccessArticle

Behaviour of Prestressed CFRP Anchorages during and after Freeze-Thaw Cycle Exposure

by Yunus Emre Harmanci, Julien Michels and Eleni Chatzi

Polymers 2018, 10(6), 565; https://doi.org/10.3390/polym10060565 - 23 May 2018

Cited by 17 | Viewed by 4101

Abstract

The long-term performance of externally-bonded reinforcements (EBR) on reinforced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect [...] Read more.

The long-term performance of externally-bonded reinforcements (EBR) on reinforced concrete (RC) structures highly depends on the behavior of constituent materials and their interfaces to various environmental loads, such as temperature and humidity exposure. Although significant efforts have been devoted to understanding the effect of such conditions on the anchorage resistance of unstressed EBR, with or without sustained loading, the effect of a released prestressing has not been thoroughly investigated. For this purpose, a series of experiments has been carried out herein, with concrete blocks strengthened with carbon fiber-reinforced polymer (CFRP) strips, both unstressed, as well as prestressed using the gradient anchorage. The gradient anchorage is a non-mechanical technique to anchor prestressed CFRP by exploiting the accelerated curing property of epoxy under higher temperatures and segment-wise prestress-force releasing. Subsequently, strengthened blocks are transferred into a chamber for exposure in dry freeze-thaw cycles (FTC). Following FTC exposure, the blocks are tested in a conventional lap-shear test setup to determine their residual anchorage resistance and then compared with reference specimens. Blocks were monitored during FTC by conventional and Fabry–Pérot-based fiber optic strain (FOS) sensors and a 3D-digital image correlation (3D-DIC) system during gradient application and lap-shear testing. Results indicate a reduction of residual anchorage resistance, stiffness and deformation capacity of the system after FTC and a change in the failure mode from concrete substrate to epoxy-concrete interface failure. It was further observed that all of these properties experienced a more significant reduction for prestressed specimens. These findings are presented with a complementary finite element model to shed more light onto the durability of such systems. Full article

(This article belongs to the Special Issue Selected Papers from "SMAR 2017")

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17 pages, 2568 KiB

Open AccessArticle

Supramolecular Hydrogel Based on pNIPAm Microgels Connected via Host–Guest Interactions

by Iurii Antoniuk, Daria Kaczmarek, Attila Kardos, Imre Varga and Catherine Amiel

Polymers 2018, 10(6), 566; https://doi.org/10.3390/polym10060566 - 23 May 2018

Cited by 36 | Viewed by 7393

Abstract

In this work, host–guest supramolecular hydrogels were prepared from poly(N-isopropylacrylamide) (pNIPAm) microgels utilizing electrostatic and host/guest self-assembly. First, pNIPAm microgels bearing a poly(acrylic acid) (pAAc) shell were coated with positively charged β-cyclodextrin polymers. Addition of adamantane-substituted dextrans (Dex-Ada) allowed us [...] Read more.

In this work, host–guest supramolecular hydrogels were prepared from poly(N-isopropylacrylamide) (pNIPAm) microgels utilizing electrostatic and host/guest self-assembly. First, pNIPAm microgels bearing a poly(acrylic acid) (pAAc) shell were coated with positively charged β-cyclodextrin polymers. Addition of adamantane-substituted dextrans (Dex-Ada) allowed us to establish interparticle connections through β-cyclodextrin-adamantane (βCD-Ada) inclusion complex formation, and thus to prepare hierarchical hydrogels. Under the conditions of hydrogel formation, close contact between the microgels was ensured. To the best of our knowledge, this is the first example of doubly crosslinked microgels prepared by noncovalent crosslinking via host–guest interactions. The prepared macrogels were studied with rheology, and fast mechanical response to temperature variation was found. Furthermore, the hydrogels exhibit fully reversible temperature-induced gel–sol transition at the physiological temperature range (37–41 °C), due to the synergetic effect between shrinking of the microgels and dissociation of βCD-Ada crosslinks at higher temperatures. This opens up attractive prospects of their potential use in biomedical applications. Full article

(This article belongs to the Special Issue Host-Guest Polymer Complexes)

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21 pages, 33224 KiB

Open AccessArticle

On the Potential of Using Dual-Function Hydrogels for Brackish Water Desalination

by Wael Ali, Beate Gebert, Sedakat Altinpinar, Thomas Mayer-Gall, Mathias Ulbricht, Jochen S. Gutmann and Karlheinz Graf

Polymers 2018, 10(6), 567; https://doi.org/10.3390/polym10060567 - 23 May 2018

Cited by 23 | Viewed by 8741

Abstract

Although current desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. We have [...] Read more.

Although current desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. We have previously reported that reversible thermally induced sorption/desorption process using polymeric hydrogels hold promise for water desalination with further development. In order to develop a more effective hydrogels architecture, polyelectrolyte moieties were introduced in this work as pendent chains and a thermally responsive polymer as network backbone using reversible addition-fragmentation chain transfer (RAFT) polymerisation. The ability of the comb-type polymeric hydrogels to desalinate water was evaluated. These hydrogels were proved to absorb water with low salinity from brine solution of 2 g L

^{- 1}

NaCl and release the absorbed water at relatively low temperature conditions of 50

^{\circ}

C. The fraction of the grafted polyacrylic acid and the comb-chain length were varied to understand their influence on the swelling/deswelling behaviour for these hydrogels. The ionic fraction in the hydrogels and the resulting hydrophilic/hydrophobic balance are crucial for the proposed desalination process. In contrast, the comb-chain length impacted the swelling behaviour of hydrogels but showed relatively little influence on the dewatering process. Full article

(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)

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12 pages, 31343 KiB

Open AccessArticle

Conductive Cotton Fabrics for Motion Sensing and Heating Applications

by Mengyun Yang, Junjie Pan, Anchang Xu, Lei Luo, Deshan Cheng, Guangming Cai, Jinfeng Wang, Bin Tang and Xungai Wang

Polymers 2018, 10(6), 568; https://doi.org/10.3390/polym10060568 - 23 May 2018

Cited by 106 | Viewed by 10225

Abstract

Conductive cotton fabric was prepared by coating single-wall carbon nanotubes (CNTs) on a knitted cotton fabric surface through a “dip-and-dry” method. The combination of CNTs and cotton fabric was analyzed using scanning electron microscopy (SEM) and Raman scattering spectroscopy. The CNTs coating improved [...] Read more.

Conductive cotton fabric was prepared by coating single-wall carbon nanotubes (CNTs) on a knitted cotton fabric surface through a “dip-and-dry” method. The combination of CNTs and cotton fabric was analyzed using scanning electron microscopy (SEM) and Raman scattering spectroscopy. The CNTs coating improved the mechanical properties of the fabric and imparted conductivity to the fabric. The electromechanical performance of the CNT-cotton fabric (CCF) was evaluated. Strain sensors made from the CCF exhibited a large workable strain range (0~100%), fast response and great stability. Furthermore, CCF-based strain sensors was used to monitor the real-time human motions, such as standing, walking, running, squatting and bending of finger and elbow. The CCF also exhibited strong electric heating effect. The flexible strain sensors and electric heaters made from CCF have potential applications in wearable electronic devices and cold weather conditions. Full article

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14 pages, 2273 KiB

Open AccessArticle

Sulfonated Poly(Arylene Ether Sulfone) and Perfluorosulfonic Acid Composite Membranes Containing Perfluoropolyether Grafted Graphene Oxide for Polymer Electrolyte Membrane Fuel Cell Applications

by Min-Young Lim and Kihyun Kim

Polymers 2018, 10(6), 569; https://doi.org/10.3390/polym10060569 - 23 May 2018

Cited by 21 | Viewed by 7806

Abstract

Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end [...] Read more.

Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end group onto the surface of GO via ring opening reaction between the carboxylic acid group in poly(hexafluoropropylene oxide) and the epoxide groups in GO, using 4-dimethylaminopyridine as a base catalyst. Both SPAES and PFSA composite membranes containing PFPE-GO showed much improved mechanical strength and dimensional stability, compared to each linear SPAES and PFSA membrane, respectively. The enhanced mechanical strength and dimensional stability of composite membranes can be ascribed to the homogeneous dispersion of rigid conjugated carbon units in GO through the increased interfacial interactions between PFPE-GO and SPAES/PFSA matrices. Full article

(This article belongs to the Collection Polyelectrolytes)

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15 pages, 2814 KiB

Open AccessArticle

Preparation of Functionalized Magnetic Fe₃O₄@Au@polydopamine Nanocomposites and Their Application for Copper(II) Removal

by Yanxia Li, Lu Huang, Wenxuan He, Yiting Chen and Benyong Lou

Polymers 2018, 10(6), 570; https://doi.org/10.3390/polym10060570 - 23 May 2018

Cited by 22 | Viewed by 6139

Abstract

Polydopamine (PDA) displays many striking properties of naturally occurring melanin in optics, electricity, and biocompatibility. Another valuable feature of polydopamine lies in its chemical structure that incorporates many functional groups such as amine, catechol and imine. In this study, a nanocomposite of magnetic [...] Read more.

Polydopamine (PDA) displays many striking properties of naturally occurring melanin in optics, electricity, and biocompatibility. Another valuable feature of polydopamine lies in its chemical structure that incorporates many functional groups such as amine, catechol and imine. In this study, a nanocomposite of magnetic Fe₃O₄@Au@polydopamine nanopaticles (Fe₃O₄@Au@ PDA MNPs) was synthesized. Carboxyl functionalized Fe₃O₄@Au nanoparticles (NPs) were successfully embedded in a layer of PDA through dopamine oxypolymerization in alkaline solution. Through the investigation of adsorption behavior to Cu(II), combined with high sensitive electrochemical detection, the as-prepared magnetic nanocomposites (MNPs) have been successfully applied in the separation and analysis of Cu(II). The experimental parameters of temperature, Cu(II) concentration and pH were optimized. Results showed that the as-prepared MNPs can reach saturation adsorption after adsorbing 2 h in neutral environment. Furthermore, the as-prepared MNPs can be easily regenerated by temperature control and exhibits a good selectivity compared to other metal ions. The prepared Fe₃O₄@Au@PDA MNPs are expected to act as a kind of adsorbent for Cu(II) deep removal from contaminated waters. Full article

(This article belongs to the Special Issue Core-Shell Structured Polymers)

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20 pages, 9734 KiB

Open AccessArticle

Development and Characterization of New Pervaporation PVA Membranes for the Dehydration Using Bulk and Surface Modifications

by Maria Dmitrenko, Anastasia Penkova, Anna Kuzminova, Alexander Missyul, Sergey Ermakov and Denis Roizard

Polymers 2018, 10(6), 571; https://doi.org/10.3390/polym10060571 - 23 May 2018

Cited by 39 | Viewed by 8007

Abstract

In the present work, the novel dense and supported membranes based on polyvinyl alcohol (PVA) with improved transport properties were developed by bulk and surface modifications. Bulk modification included the blending of PVA with chitosan (CS) and the creation of a mixed-matrix membrane [...] Read more.

In the present work, the novel dense and supported membranes based on polyvinyl alcohol (PVA) with improved transport properties were developed by bulk and surface modifications. Bulk modification included the blending of PVA with chitosan (CS) and the creation of a mixed-matrix membrane by introduction of fullerenol. This significantly altered the internal structure of PVA membrane, which led to an increase in permeability with high selectivity to water. Surface modification of the developed modified dense membranes, based on composites PVA-CS and PVA-fullerenol-CS, was performed through (i) making of a supported membrane with a thin selective composite layer and (ii) applying of the layer-by-layer assembly (LbL) method for coating of nano-sized polyelectrolyte (PEL) layers to increase the membrane productivity. The nature of polyelectrolyte type—(poly(allylamine hydrochloride) (PAH), poly(sodium 4-styrenesulfonate) (PSS), poly(acrylic acid) (PAA), CS), and number of PEL bilayers (2–10)—were studied. The structure of the composite membranes was investigated by FTIR, X-ray diffraction, and SEM. Transport properties were studied during the pervaporation separation of 80% isopropanol–20% water mixture. It was shown that supported membrane consisting of hybrid layer of PVA-fullerenol (5%)–chitosan (20%) with five polyelectrolyte bilayers (PSS, CS) deposited on it had the best transport properties. Full article

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12 pages, 12024 KiB

Open AccessArticle

Multi-Jet Electrospinning with Auxiliary Electrode: The Influence of Solution Properties

by Yu-Ke Wu, Liang Wang, Jie Fan, Wan Shou, Bao-Ming Zhou and Yong Liu

Polymers 2018, 10(6), 572; https://doi.org/10.3390/polym10060572 - 23 May 2018

Cited by 32 | Viewed by 5930

Abstract

Multiple jets ejection in electrospinning has been a major approach to achieving a high production rate of ultrafine fibers, also known as nanofibers. This work studies the effect of solution parameters—including dielectric constant, polarity, conductivity and surface tension—on the jet number and jet [...] Read more.

Multiple jets ejection in electrospinning has been a major approach to achieving a high production rate of ultrafine fibers, also known as nanofibers. This work studies the effect of solution parameters—including dielectric constant, polarity, conductivity and surface tension—on the jet number and jet evolution in the auxiliary electrode electrospinning approach. The results show that it is easier to generate 2–6 jets with short stable jet length (1.7–6.9 mm) under low voltage (5.03–7.13 kV) when solutions have higher dielectric constant (32.2–78.6) and larger surface tension (31.8–41.29 mN/m). The influence of solution properties on stable jet length and the influence of applied voltage to produce multiple jets are discussed in detail. This work provides a new perspective for understanding jet evolution and mass production of nanofibers in electrospinning. Full article

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14 pages, 7070 KiB

Open AccessArticle

Electrospun Polyethylene Terephthalate Nonwoven Reinforced Polypropylene Separator: Scalable Synthesis and Its Lithium Ion Battery Performance

by Haopeng Cai, Xing Tong, Kai Chen, Yafei Shen, Jiashun Wu, Yinyu Xiang, Zhao Wang and Junsheng Li

Polymers 2018, 10(6), 574; https://doi.org/10.3390/polym10060574 - 23 May 2018

Cited by 39 | Viewed by 7514

Abstract

A novel polyethylene terephthalate nonwoven reinforced polypropylene composite separator (PET/PP) with high thermal stability and low thermal shrinkage characteristic is developed through a scalable production process. In the composite separator, the electronspun polyethylene terephthalate nonwoven layer improves the electrolyte affinity and can sustain [...] Read more.

A novel polyethylene terephthalate nonwoven reinforced polypropylene composite separator (PET/PP) with high thermal stability and low thermal shrinkage characteristic is developed through a scalable production process. In the composite separator, the electronspun polyethylene terephthalate nonwoven layer improves the electrolyte affinity and can sustain as the barrier layer after the shutdown of the polypropylene layer. Due to its high ionic conductivity, the PET/PP separator shows an excellent discharge capacity. In addition, the superior thermal stability of the separator significantly enhances the safety performance of the separator. Considering the feasibility of the large-scale production of the PET/PP separator and its superior battery performance, we expect that the novel separator could be a promising alternative to the existing commercial separators. Full article

(This article belongs to the Special Issue Polymeric Materials for Electrochemical Energy Conversion and Storage)

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13 pages, 4706 KiB

Open AccessArticle

A Sandwich-Structured Piezoresistive Sensor with Electrospun Nanofiber Mats as Supporting, Sensing, and Packaging Layers

by Zicong Zhao, Bintian Li, Liqun Xu, Yan Qiao, Feng Wang, Qingyou Xia and Zhisong Lu

Polymers 2018, 10(6), 575; https://doi.org/10.3390/polym10060575 - 23 May 2018

Cited by 37 | Viewed by 7858

Abstract

Electrospun nanofiber mats have been used as sensing elements to construct piezoresistive devices due to their large surface area and high porosity. However, they have not been utilized as skin-contact supporting layers to package conductive nanofiber networks for the fabrication of piezoresistive sensors. [...] Read more.

Electrospun nanofiber mats have been used as sensing elements to construct piezoresistive devices due to their large surface area and high porosity. However, they have not been utilized as skin-contact supporting layers to package conductive nanofiber networks for the fabrication of piezoresistive sensors. In this work, we developed a sandwich-structured pressure sensor, which can sensitively monitor human motions and vital signs, with electrospun nanofiber mats as supporting, sensing, and packaging layers. The nanofiber mats were prepared by electrospinning with biocompatible poly (l-lactide) (PLA), silk fibroin (SF), and collagen (COL) as raw materials. The synthesized PLA–SF–COL mat possesses a non-woven structure with a fiber diameter of 122 ± 28 nm and a film thickness of 37 ± 5.3 μm. Polypyrrole (PPy) nanoparticles were grown in-situ on the mat to form a conductive layer. After stacking the pristine and conductive mats to form a PLA–SF–COL mat/(PPy-coated mat)₂ structure, another layer was electrospun to pack the multilayers for the construction of a sandwich-structured piezoresistive sensor. The as-prepared device can sensitively detect external pressures caused by coin loading and finger tapping/pressing. It can also tolerate more than 600 times of pressing without affecting its sensing capability. The human body-attached experiments further demonstrate that the sensor could real-time monitor finger/arm bending, arterial pulse, respiration rate, and speaking-caused throat vibration. The electrospinning-based fabrication may be used as a facile and low-cost strategy to produce flexible piezoresistive sensors with excellent skin-compatibility and great pressure sensing capability. Full article

(This article belongs to the Special Issue Soft Materials and Systems)

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16 pages, 23932 KiB

Open AccessArticle

Thermoadaptive Supramolecular α-Cyclodextrin Crystallization-Based Hydrogels via Double Hydrophilic Block Copolymer Templating

by Tingting Li, Baris Kumru, Noah Al Nakeeb, Jochen Willersinn and Bernhard V. K. J. Schmidt

Polymers 2018, 10(6), 576; https://doi.org/10.3390/polym10060576 - 23 May 2018

Cited by 20 | Viewed by 5730

Abstract

Supramolecular hydrogels play a prominent role in contemporary research of hydrophilic polymers. Especially, hydrogels based on α-cyclodextrin/poly(ethylene glycol) (α-CD/PEG) complexation and crystal formation are studied frequently. Here, the effect of double hydrophilic block copolymers (DHBCs) on α-CD/PEG hydrogel properties is investigated. Therefore, a [...] Read more.

Supramolecular hydrogels play a prominent role in contemporary research of hydrophilic polymers. Especially, hydrogels based on α-cyclodextrin/poly(ethylene glycol) (α-CD/PEG) complexation and crystal formation are studied frequently. Here, the effect of double hydrophilic block copolymers (DHBCs) on α-CD/PEG hydrogel properties is investigated. Therefore, a novel DHBC, namely poly(N-vinylpyrrolidone)-b-poly(oligo ethylene glycol methacrylate) (PVP-b-POEGMA), was synthesized via a combination of reversible deactivation radical polymerization and modular conjugation methods. In the next step, hydrogel formation was studied after α-CD addition. Interestingly, DHBC-based hydrogels showed a significant response to thermal history. Heating of the gels to different temperatures led to different mechanical properties after cooling to ambient temperature, i.e., gels with mechanical properties similar to the initial gels or weak flowing gels were obtained. Thus, the hydrogels showed thermoadaptive behavior, which might be an interesting property for future applications in sensing. Full article

(This article belongs to the Special Issue Hydrophilic Polymers)

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29 pages, 3762 KiB

Open AccessArticle

Precise Synthesis, Properties, and Structures of Cyclic Poly(ε-caprolactone)s

by Li Xiang, Wonyeong Ryu, Heesoo Kim and Moonhor Ree

Polymers 2018, 10(6), 577; https://doi.org/10.3390/polym10060577 - 23 May 2018

Cited by 24 | Viewed by 6089

Abstract

Cyclic PCL (c-PCL) has drawn great attention from academia and industry because of its unique, unusual structure and property characteristics due to the absence of end groups in addition to the biocompatibility and biodegradability of its linear analogue. As a result [...] Read more.

Cyclic PCL (c-PCL) has drawn great attention from academia and industry because of its unique, unusual structure and property characteristics due to the absence of end groups in addition to the biocompatibility and biodegradability of its linear analogue. As a result of much research effort, several synthetic methods have been developed to produce c-PCLs so far. Their chain, morphology and property characteristics were investigated even though carried out on a very limited basis. This feature article reviews the research progress made in the synthesis, morphology, and properties of c-PCL; all results and their pros and cons are discussed in terms of purity and molecular weight distribution in addition to the cyclic topology effect. In addition, we attempted to synthesize a series of c-PCL products of high purity by using intramolecular azido-alkynyl click cyclization chemistry and subsequent precise and controlled separation and purification; and their thermal degradation and phase transitions were investigated in terms of the cyclic topology effect. Full article

(This article belongs to the Special Issue Cyclic Polymers)

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8 pages, 1284 KiB

Open AccessArticle

Determination of Pressure Dependence of Polymer Phase Transitions by pVT Analysis

by Jürgen Pionteck

Polymers 2018, 10(6), 578; https://doi.org/10.3390/polym10060578 - 24 May 2018

Cited by 25 | Viewed by 7706

Abstract

Glass transitions, melting, crystallization, and the isotropization of polymers are connected with changes in the density, respectively the specific volume (V_sp), which can be analyzed by dilatometric methods. Here, the pressure dependence of such transitions is determined by pressure volume temperature [...] Read more.

Glass transitions, melting, crystallization, and the isotropization of polymers are connected with changes in the density, respectively the specific volume (V_sp), which can be analyzed by dilatometric methods. Here, the pressure dependence of such transitions is determined by pressure volume temperature (pVT) analysis for different thermoplastic polymers in the pressure range of 10 to 200 MPa, and the temperature range from room temperature to 350 °C. The values for ambient pressure are extrapolated. It is shown that polymer transitions always increase with pressure, and that the melting temperature and glass transition temperature are nearly linearly dependent on pressure. This information, as well as the observed density changes with pressure and temperature, is very important for the processing of thermoplastics, including their simulation, as well as for the thermodynamic interpretations of the transition’s nature. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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18 pages, 5996 KiB

Open AccessArticle

Novel PEG-Modified Hybrid PLGA-Vegetable Oils Nanostructured Carriers for Improving Performances of Indomethacin Delivery

by Jana Ghitman, Raluca Stan, Adi Ghebaur, Sergiu Cecoltan, Eugeniu Vasile and Horia Iovu

Polymers 2018, 10(6), 579; https://doi.org/10.3390/polym10060579 - 24 May 2018

Cited by 30 | Viewed by 5043

Abstract

The purpose of this work was to more exhaustively study the influence of nanocarrier matrix composition and also the polyethylene glycol (PEG)-modified surface on the performances of formulations as lipophilic drug delivery systems. Poly (d,l-lactide-co-glycolide), two vegetable [...] Read more.

The purpose of this work was to more exhaustively study the influence of nanocarrier matrix composition and also the polyethylene glycol (PEG)-modified surface on the performances of formulations as lipophilic drug delivery systems. Poly (d,l-lactide-co-glycolide), two vegetable oils (Nigella sativa oil and Echium oil) and indomethacin were employed to prepare novel PEG-coated nanocarriers through emulsion solvent evaporation method. The surface modification was achieved by physical PEG adsorption (in the post-production step). Transmission electron microscopy (TEM) nanographs highlighted the core-shell structure of hybrid formulations while scanning electron microscopy (SEM) images showed no obvious morphological changes after PEG adsorption. Drug loading (DL) and entrapment efficiency (EE) varied from 4.6% to 16.4% and 28.7% to 61.4%, solely depending on the type of polymeric matrix. The oil dispersion within hybrid matrix determined a more amorphous structure, as was emphasized by differential scanning calorimetry (DSC) investigations. The release studies highlighted the oil effect upon the ability of nanocarrier to discharge in a more sustained manner the encapsulated drug. Among the kinetic models employed, the Weibull and Korsmeyer-Peppas models showed the better fit (R² = 0.999 and 0.981) with n < 0.43 indicating a Fickian type release pattern. According to cytotoxic assessment the PEG presence on the surface increased the cellular viability with ~1.5 times as compared to uncoated formulations. Full article

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17 pages, 5202 KiB

Open AccessArticle

Preparation, Physicochemical Properties and Hemocompatibility of Biodegradable Chitooligosaccharide-Based Polyurethane

by Weiwei Xu, Minghui Xiao, Litong Yuan, Jun Zhang and Zhaosheng Hou

Polymers 2018, 10(6), 580; https://doi.org/10.3390/polym10060580 - 24 May 2018

Cited by 24 | Viewed by 4180

Abstract

The purpose of this study was to develop a process to achieve biodegradable chitooligosaccharide-based polyurethane (CPU) with improved hemocompatibility and mechanical properties. A series of CPUs with varying chitooligosaccharide (COS) content were prepared according to the conventional two-step method. First, the prepolymer was [...] Read more.

The purpose of this study was to develop a process to achieve biodegradable chitooligosaccharide-based polyurethane (CPU) with improved hemocompatibility and mechanical properties. A series of CPUs with varying chitooligosaccharide (COS) content were prepared according to the conventional two-step method. First, the prepolymer was synthesized from poly(ε-caprolactone) (PCL) and uniform-size diurethane diisocyanates (HBH). Then, the prepolymer was chain-extended by COS in N,N-dimethylformamide (DMF) to obtain the weak-crosslinked CPU, and the corresponding films were obtained from the DMF solution by the solvent evaporation method. The uniform-size hard segments and slight crosslinking of CPU were beneficial for enhancing the mechanical properties, which were one of the essential requirements for long-term implant biomaterials. The chemical structure was characterized by FT-IR, and the influence of COS content in CPU on the physicochemical properties and hemocompatibility was extensively researched. The thermal stability studies indicated that the CPU films had lower initial decomposition temperature and higher maximum decomposition temperature than pure polyurethane (CPU-1.0) film. The ultimate stress, initial modulus, and surface hydrophilicity increased with the increment of COS content, while the strain at break and water absorption decreased, which was due to the increment of crosslinking density. The results of in vitro degradation signified that the degradation rate increased with the increasing content of COS in CPU, demonstrating that the degradation rate could be controlled by adjusting COS content. The surface hemocompatibility was examined by protein adsorption and platelet adhesion tests. It was found that the CPU films had improved resistance to protein adsorption and possessed good resistance to platelet adhesion. The slow degradation rate and good hemocompatibility of the CPUs showed great potential in blood-contacting devices. In addition, many active amino and hydroxyl groups contained in the structure of CPU could carry out further modification, which made it an excellent candidate for wide application in biomedical field. Full article

(This article belongs to the Special Issue Intrinsically Biocompatible Polymer Systems)

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16 pages, 2663 KiB

Open AccessArticle

Novel Bacterial Cellulose/Gelatin Hydrogels as 3D Scaffolds for Tumor Cell Culture

by Jing Wang, Li Zhao, Aixia Zhang, Yuan Huang, Javad Tavakoli and Youhong Tang

Polymers 2018, 10(6), 581; https://doi.org/10.3390/polym10060581 - 24 May 2018

Cited by 55 | Viewed by 8022

Abstract

Three-dimensional (3D) cells in vitro culture are becoming increasingly popular in cancer research because some important signals are lost when cells are cultured in a two-dimensional (2D) substrate. In this work, bacterial cellulose (BC)/gelatin hydrogels were successfully synthesized and were investigated as scaffolds [...] Read more.

Three-dimensional (3D) cells in vitro culture are becoming increasingly popular in cancer research because some important signals are lost when cells are cultured in a two-dimensional (2D) substrate. In this work, bacterial cellulose (BC)/gelatin hydrogels were successfully synthesized and were investigated as scaffolds for cancer cells in vitro culture to simulate tumor microenvironment. Their properties and ability to support normal growth of cancer cells were evaluated. In particular, the human breast cancer cell line (MDA-MD-231) was seeded into BC/gelatin scaffolds to investigate their potential in 3D cell in vitro culture. MTT proliferation assay, scanning electron microscopy, hematoxylin and eosin staining and immunofluorescence were used to determine cell proliferation, morphology, adhesion, infiltration, and receptor expression. The in vitro MDA-MD-231 cell culture results demonstrated that cells cultured on the BC/gelatin scaffolds had significant adhesion, proliferation, ingrowth and differentiation. More importantly, MDA-MD-231 cells cultured in BC/gelatin scaffolds retained triple-negative receptor expression, demonstrating that BC/gelatin scaffolds could be used as ideal in vitro culture scaffolds for tumor cells. Full article

(This article belongs to the Collection Polysaccharides)

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15 pages, 3953 KiB

Open AccessArticle

Microwave Attenuation of Graphene Modified Thermoplastic Poly(Butylene adipate-co-terephthalate) Nanocomposites

by Sima Kashi, S. Ali Hadigheh and Russell Varley

Polymers 2018, 10(6), 582; https://doi.org/10.3390/polym10060582 - 25 May 2018

Cited by 27 | Viewed by 4683

Abstract

With the widespread development and use of electronics and telecommunication devices, electromagnetic radiation has emerged as a new pollution. In this study, we fabricated flexible multifunctional nanocomposites by incorporating graphene nanoplatelets into a soft thermoplastic matrix and investigated its performance in attenuating electromagnetic [...] Read more.

With the widespread development and use of electronics and telecommunication devices, electromagnetic radiation has emerged as a new pollution. In this study, we fabricated flexible multifunctional nanocomposites by incorporating graphene nanoplatelets into a soft thermoplastic matrix and investigated its performance in attenuating electromagnetic radiation over frequency ranges of C (5.85–8.2 GHz), X (8.2–12.4 GHz), and Ku bands (12.4–18 GHz). Effects of nanofiller loading, sample thickness, and radiation frequency on the nanocomposites shielding effectiveness (SE) were investigated via experimental measurements and simulation. The highest rate of increase in SE was observed near percolation threshold of graphene. Comparison of reflectivity and absorptivity revealed that reflection played a major role in nanocomposites shielding potential for all frequencies while the low absorptivity was due to high power reflection at nanocomposite surface and thin thickness. Subsequently, effective absorbance calculations revealed the great potential of nanocomposites for absorbing microwaves, reaching more than 80%. Simulations confirmed the observed nanocomposites SE behaviours versus frequency. Depending on thickness, different frequency dependency behaviours were observed; for thin samples, SE remained unchanged, while for thicker samples it exhibited either increasing or decreasing trends with increasing frequency. At any fixed frequency, increasing the thickness resulted in sine-wave periodic changes in SE with a general increasing trend. Full article

(This article belongs to the Special Issue Smart and Modern Thermoplastic Polymer Materials)

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13 pages, 5889 KiB

Open AccessArticle

Soy-Based Soft Matrices for Encapsulation and Delivery of Hydrophilic Compounds

by Ruvimbo Chitemere, Shane Stafslien, Long Jiang, Dean Webster and Mohiuddin Quadir

Polymers 2018, 10(6), 583; https://doi.org/10.3390/polym10060583 - 26 May 2018

Cited by 3 | Viewed by 3795

Abstract

A new controlled-release platform for hydrophilic compounds has been developed, utilizing citric acid-cured epoxidized sucrose soyate (ESS) as the matrix forming material. By cross-linking epoxy groups of ESS with citric acid in the presence of a hydrophilic model molecule, sodium salt of fluorescein [...] Read more.

A new controlled-release platform for hydrophilic compounds has been developed, utilizing citric acid-cured epoxidized sucrose soyate (ESS) as the matrix forming material. By cross-linking epoxy groups of ESS with citric acid in the presence of a hydrophilic model molecule, sodium salt of fluorescein (Sod-FS), we were able to entrap the latter homogenously within the ESS matrix. No chemical change of the entrapped active agent was evident during the fabrication process. Hydrophobicity of the matrix was found to be the rate-limiting factor for sustaining the release of the hydrophilic model compound, while inclusion of release-modifiers such as poly(ethylene glycol) (PEG) within the matrix system modulated the rate and extent of guest release. Using 5 kDa PEG at 5% w/w of the total formulation, it was possible to extend the release of the active ingredient for more than a month. In addition, the amount of modifiers in formulations also influenced the mechanical properties of the matrices, including loss and storage modulus. Mechanism of active release from ESS matrices was also evaluated using established kinetic models. Formulations composed entirely of ESS showed a non-Fickian (anomalous) release behavior while Fickian (Case I) transport was the predominant mechanism of active release from ESS systems containing different amount of PEGs. The mean dissolution time (MDT) of the hydrophilic guest molecule from within the ESS matrix was found to be a function of the molecular weight and the amount of PEG included. At the molecular level, we observed no cellular toxicities associated with ESS up to a concentration level of 10 μM. We envision that such fully bio-based matrices can find applications in compounding point-of-care, extended-release formulations of highly water-soluble active agents. Full article

(This article belongs to the Special Issue Polymers for Therapy and Diagnostics)

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16 pages, 7376 KiB

Open AccessArticle

Enhancing the Silanization Reaction of the Silica-Silane System by Different Amines in Model and Practical Silica-Filled Natural Rubber Compounds

by C. Hayichelaeh, L.A.E.M. Reuvekamp, W.K. Dierkes, A. Blume, J.W.M. Noordermeer and K. Sahakaro

Polymers 2018, 10(6), 584; https://doi.org/10.3390/polym10060584 - 27 May 2018

Cited by 52 | Viewed by 13064

Abstract

Diphenyl guanidine (DPG) is an essential ingredient in silica-reinforced rubber compounds for low rolling resistance tires, as it not only acts as a secondary accelerator, but also as a catalyst for the silanization reaction. However, because of concern over the toxicity of DPG [...] Read more.

Diphenyl guanidine (DPG) is an essential ingredient in silica-reinforced rubber compounds for low rolling resistance tires, as it not only acts as a secondary accelerator, but also as a catalyst for the silanization reaction. However, because of concern over the toxicity of DPG that liberates aniline during high-temperature processing, safe alternatives are required. The present work studies several amines as potential alternatives for DPG. Different amines (i.e., hexylamine, decylamine, octadecylamine, cyclohexylamine, dicyclohexylamine, and quinuclidine) are investigated in a model system, as well as in a practical rubber compound by taking the ones with DPG and without amine as references. The kinetics of the silanization reaction of the silica/silane mixtures are evaluated using model compounds. The mixtures with amines show up to 3.7 times higher rate constants of the primary silanization reaction compared to the compound without amine. Linear aliphatic amines promote the rate constant of the primary silanization reaction to a greater extent compared to amines with a cyclic structure. The amines with short-alkyl chains that provide better accessibility towards the silica surface, enhance the primary silanization reaction more than the ones with long-alkyl chains. The different amines have no significant influence on the rate constant of the secondary silanization reaction. The amine types that give a higher primary silanization reaction rate constant show a lower flocculation rate in the practical compounds. For the systems with a bit lower primary silanization reaction rate, but higher extent of shielding or physical adsorption that still promotes higher interfacial compatibility between the elastomer and the filler surface, the rubber compounds show a lower Payne effect which would indicate lower filler-filler interaction. However, the flocculation rate constant remained high. Full article

(This article belongs to the Special Issue Elastomers)

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11 pages, 4370 KiB

Open AccessArticle

Novel Magnetic-to-Thermal Conversion and Thermal Energy Management Composite Phase Change Material

by Xiaoqiao Fan, Jinqiu Xiao, Wentao Wang, Yuang Zhang, Shufen Zhang and Bingtao Tang

Polymers 2018, 10(6), 585; https://doi.org/10.3390/polym10060585 - 27 May 2018

Cited by 38 | Viewed by 5190

Abstract

Superparamagnetic materials have elicited increasing interest due to their high-efficiency magnetothermal conversion. However, it is difficult to effectively manage the magnetothermal energy due to the continuous magnetothermal effect at present. In this study, we designed and synthesized a novel Fe₃O₄ [...] Read more.

Superparamagnetic materials have elicited increasing interest due to their high-efficiency magnetothermal conversion. However, it is difficult to effectively manage the magnetothermal energy due to the continuous magnetothermal effect at present. In this study, we designed and synthesized a novel Fe₃O₄/PEG/SiO₂ composite phase change material (PCM) that can simultaneously realize magnetic-to-thermal conversion and thermal energy management because of outstanding thermal energy storage ability of PCM. The composite was fabricated by in situ doping of superparamagnetic Fe₃O₄ nanoclusters through a simple sol–gel method. The synthesized Fe₃O₄/PEG/SiO₂ PCM exhibited good thermal stability, high phase change enthalpy, and excellent shape-stabilized property. This study provides an additional promising route for application of the magnetothermal effect. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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10 pages, 3690 KiB

Open AccessArticle

High Permittivity Nanocomposites Embedded with Ag/TiO₂ Core–Shell Nanoparticles Modified by Phosphonic Acid

by Xizi Chen, Fei Liang, Wenzhong Lu, Zheng Jin, Yifei Zhao and Ming Fu

Polymers 2018, 10(6), 586; https://doi.org/10.3390/polym10060586 - 27 May 2018

Cited by 16 | Viewed by 4289

Abstract

In this paper, nanocomposites that contain core-shell Ag/TiO₂ particles as the filler and polytetrafluoroethylene (PTFE) as the matrix were investigated. Two surfactants, namely octyl phosphonic acid (OPA) and pentafluorobenzyl phosphonic acid (PFBPA), were applied to modify Ag/TiO₂ fillers for uniform dispersion [...] Read more.

In this paper, nanocomposites that contain core-shell Ag/TiO₂ particles as the filler and polytetrafluoroethylene (PTFE) as the matrix were investigated. Two surfactants, namely octyl phosphonic acid (OPA) and pentafluorobenzyl phosphonic acid (PFBPA), were applied to modify Ag/TiO₂ fillers for uniform dispersion in the matrix. Fourier transform infrared spectroscopy analysis of bonds between the TiO₂ shells and the phosphonic modifiers shows Ti–O–P chemical bonding between the Ag/TiO₂ fillers and the modifiers. Thermogravimetric analysis results show a superior adsorption effect of PFBPA over OPA on the Ag/TiO₂ filler surface at the same weight percentage. For nanocomposites that contain modified Ag/TiO₂ nanoparticles, the loss was reduced despite the high permittivity at the same loading. The permittivity of the nanocomposites by PFBPA is larger than that of OPA, because the more uniform dispersion of inorganic particles in the PTFE matrix enhances the interfacial polarization effect. The mechanism of enhanced dielectric performance was studied and discussed. Full article

(This article belongs to the Special Issue Polymer Hybrids and Composites)

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13 pages, 3024 KiB

Open AccessArticle

High-Performance Pressure Sensor for Monitoring Mechanical Vibration and Air Pressure

by Yancheng Meng, Hongwei Li, Kunjie Wu, Suna Zhang and Liqiang Li

Polymers 2018, 10(6), 587; https://doi.org/10.3390/polym10060587 - 27 May 2018

Cited by 12 | Viewed by 5708

Abstract

To realize the practical applications of flexible pressure sensors, the high performance (sensitivity and response time) as well as more functionalities are highly desired. In this work, we fabricated a piezoresistive pressure sensor based on the micro-structured composites films of multi-walled carbon nanotubes [...] Read more.

To realize the practical applications of flexible pressure sensors, the high performance (sensitivity and response time) as well as more functionalities are highly desired. In this work, we fabricated a piezoresistive pressure sensor based on the micro-structured composites films of multi-walled carbon nanotubes (MWCNTs) and poly (dimethylsiloxane) (PDMS). In addition, we establish efficient strategies to improve key performance of our pressure sensor. Its sensitivity is improved up to 474.13 kPa⁻¹ by minimizing pressure independent resistance of sensor, and response time is shorten as small as 2 μs by enhancing the elastic modulus of polymer elastomer. Benefiting from the high performance, the functionalities of sensors are successfully extended to the accurate detection of high frequency mechanical vibration (~300 Hz) and large range of air pressure (6–101 kPa), both of which are not achieved before. Full article

(This article belongs to the Special Issue Soft Materials and Systems)

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11 pages, 2780 KiB

Open AccessArticle

Effect of Xanthan–Chitosan Microencapsulation on the Survival of Lactobacillus acidophilus in Simulated Gastrointestinal Fluid and Dairy Beverage

by Guowei Shu, Yunxia He, Li Chen, Yajuan Song, Jili Cao and He Chen

Polymers 2018, 10(6), 588; https://doi.org/10.3390/polym10060588 - 28 May 2018

Cited by 19 | Viewed by 4424

Abstract

Lactobacillus acidophilus was encapsulated in xanthan–chitosan (XC) and xanthan–chitosan–xanthan (XCX) polyelectrolyte complex (PEC) gels by extrusion method. The obtained capsules were characterized by X-ray diffraction and FTIR spectroscopy. The effects of microencapsulation on the changes in survival and release behavior of the Lactobacillus [...] Read more.

Lactobacillus acidophilus was encapsulated in xanthan–chitosan (XC) and xanthan–chitosan–xanthan (XCX) polyelectrolyte complex (PEC) gels by extrusion method. The obtained capsules were characterized by X-ray diffraction and FTIR spectroscopy. The effects of microencapsulation on the changes in survival and release behavior of the Lactobacillus acidophilus during exposure to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were studied. Encapsulated Lactobacillus acidophilus exhibited a significantly higher resistance to SGF and SIF than non-encapsulated samples. In addition, the viability of free and immobilized cells of Lactobacillus acidophilus incorporated into dairy beverages was assessed for 21 days both at room temperature and in refrigerated storage. The results indicated that xanthan–chitosan–xanthan (XCX) and xanthan–chitosan (XC) significantly (p < 0.05) improved the cell survival of Lactobacillus acidophilus in yogurt during 21 days of storage at 4 and 25 °C, when compared to free cells. Full article

(This article belongs to the Collection Polysaccharides)

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9 pages, 1488 KiB

Open AccessCommunication

Size-Controllable Enzymatic Synthesis of Short Hairpin RNA Nanoparticles by Controlling the Rate of RNA Polymerization

by Hyejin Kim, Dajeong Kim, Jaepil Jeong, Hyunsu Jeon and Jong Bum Lee

Polymers 2018, 10(6), 589; https://doi.org/10.3390/polym10060589 - 28 May 2018

Cited by 9 | Viewed by 5114

Abstract

Thanks to a wide range of biological functions of RNA, and advancements in nanotechnology, RNA nanotechnology has developed in multiple ways for RNA-based therapeutics. In particular, among RNA engineering techniques, enzymatic self-assembly of RNA structures has gained great attention for its high packing [...] Read more.

Thanks to a wide range of biological functions of RNA, and advancements in nanotechnology, RNA nanotechnology has developed in multiple ways for RNA-based therapeutics. In particular, among RNA engineering techniques, enzymatic self-assembly of RNA structures has gained great attention for its high packing density of RNA, with a low cost and one-pot synthetic process. However, manipulation of the overall size of particles, especially a reduction in size, has not been studied in depth. Here, we reported the enzymatic self-assembly of short hairpin RNA particles for the downregulation of target genes, and a rational approach to the manipulation of the resultant particle size. This is the first report of the size-controllable enzymatic self-assembly of short hairpin RNA nanoparticles. While keeping all the benefits of an enzymatic approach, the overall size of the RNA particles was controlled on a scale of 2 μm to 100 nm, falling within the therapeutically applicable size range. Full article

(This article belongs to the Special Issue Polymerization Kinetics)

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11 pages, 3874 KiB

Open AccessArticle

Adsorption Behavior of Polymer Chain with Different Topology Structure at the Polymer-Nanoparticle Interface

by Qingliang Song, Yongyun Ji, Shiben Li, Xianghong Wang and Linli He

Polymers 2018, 10(6), 590; https://doi.org/10.3390/polym10060590 - 28 May 2018

Cited by 9 | Viewed by 5281

Abstract

The effect of the polymer chain topology structure on the adsorption behavior in the polymer-nanoparticle (NP) interface is investigated by employing coarse-grained molecular dynamics simulations in various polymer-NP interaction and chain stiffness. At a weak polymer-NP interaction, ring chain with a closed topology [...] Read more.

The effect of the polymer chain topology structure on the adsorption behavior in the polymer-nanoparticle (NP) interface is investigated by employing coarse-grained molecular dynamics simulations in various polymer-NP interaction and chain stiffness. At a weak polymer-NP interaction, ring chain with a closed topology structure has a slight priority to occupy the interfacial region than linear chain. At a strong polymer-NP interaction, the “middle” adsorption mechanism dominates the polymer local packing in the interface. As the increase of chain stiffness, an interesting transition from ring to linear chain preferential adsorption behavior occurs. The semiflexible linear chain squeezes ring chain out of the interfacial region by forming a helical structure and wrapping tightly the surface of NP. In particular, this selective adsorption behavior becomes more dramatic for the case of rigid-like chain, in which 3D tangent conformation of linear chain is absolutely prior to the 2D plane orbital structure of ring chain. The local packing and competitive adsorption behavior of bidisperse matrix in polymer-NP interface can be explained based on the adsorption mechanism of monodisperse (pure ring or linear) case. These investigations may provide some insights into polymer-NP interfacial adsorption behavior and guide the design of high-performance nanocomposites. Full article

(This article belongs to the Special Issue Nanoparticle-Reinforced Polymers)

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11 pages, 4448 KiB

Open AccessArticle

Promoting Barrier Performance and Cathodic Protection of Zinc-Rich Epoxy Primer via Single-Layer Graphene

by Jingrong Liu, Tao Liu, Zhangwei Guo, Na Guo, Yanhua Lei, Xueting Chang and Yansheng Yin

Polymers 2018, 10(6), 591; https://doi.org/10.3390/polym10060591 - 28 May 2018

Cited by 46 | Viewed by 6597

Abstract

The effect of single-layer graphene sheets (Gr) on the corrosion protection of zinc-rich epoxy primers (ZRPs) was investigated. Scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) were used to characterize morphology and composition of the coatings after immersion for 25 days. [...] Read more.

The effect of single-layer graphene sheets (Gr) on the corrosion protection of zinc-rich epoxy primers (ZRPs) was investigated. Scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) were used to characterize morphology and composition of the coatings after immersion for 25 days. The cross-sectional SEM images and X-ray photoelectron spectroscopy (XPS) confirmed that the addition of single-layer graphene facilitated assembling of zinc oxides on the interface between the coating and the steel. The open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) measurements revealed that both the cathodic protection and barrier performance of the ZRP were enhanced after addition of 0.6 wt. % Gr (Gr0.6-ZRP). In addition, the cathodic protection property of the Gr0.6-ZRP was characterized quantitatively by localized electrochemical impedance spectroscopy (LEIS) in the presence of an artificial scratch on the coating. The results demonstrate that moderate amounts of single-layer graphene can significantly improve corrosion resistance of ZRP, due to the barrier protection and cathodic protection effects. Full article

(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)

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15 pages, 3923 KiB

Open AccessArticle

Thermo-Responsive Cellulose-Based Material with Switchable Wettability for Controllable Oil/Water Separation

by Wenbo Chen, Hui He, Hongxiang Zhu, Meixiao Cheng, Yunhua Li and Shuangfei Wang

Polymers 2018, 10(6), 592; https://doi.org/10.3390/polym10060592 - 28 May 2018

Cited by 141 | Viewed by 6998

Abstract

A thermo-responsive cellulose-based material (cellulose-g-PNIPAAm) was prepared by grafting N-isopropylacrylamide (NIPAAm) onto bagasse pulp cellulose via Ce (IV)-initiated free radical polymerization. The surfaces of the obtained cellulose-g-PNIPAAm paper showed a rapid wettability conversion from being hydrophilic (water contact [...] Read more.

A thermo-responsive cellulose-based material (cellulose-g-PNIPAAm) was prepared by grafting N-isopropylacrylamide (NIPAAm) onto bagasse pulp cellulose via Ce (IV)-initiated free radical polymerization. The surfaces of the obtained cellulose-g-PNIPAAm paper showed a rapid wettability conversion from being hydrophilic (water contact angles (WCA) of 0°) at 25 °C to becoming hydrophobic (WCA of 134.2°) at 45 °C. Furthermore, the thermo-responsive mechanism of cellulose-g-PNIPAAm was examined by the in situ variable-temperature ¹³C NMR, ¹H NMR and AFM analysis. At the same time, the resulting cellulose paper was applied for a switchable separation of oil/water mixtures. Water can pass through the paper under 45 °C, while oil is kept on the paper. When the temperature is above 45 °C, oil can permeate through the paper, while water cannot pass through the water. Moreover, the paper exhibited excellent regeneration performance after five cycles and maintained its switchable wettability. Full article

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15 pages, 6458 KiB

Open AccessArticle

Rheology, Non-Isothermal Crystallization Behavior, Mechanical and Thermal Properties of PMMA-Modified Carbon Fiber-Reinforced Poly(Ethylene Terephthalate) Composites

by Guoliang Lin, Dongwei Li, Minyi Liu, Xiaoyi Zhang and Yuying Zheng

Polymers 2018, 10(6), 594; https://doi.org/10.3390/polym10060594 - 29 May 2018

Cited by 16 | Viewed by 4475

Abstract

Poly(ethylene terephthalate) (PET) composites containing carbon fiber (CF) or polymethyl methacrylate (PMMA)-grafted carbon fiber (PMMA-g-CF) were prepared by melt compounding. The rheology, non-isothermal crystallization behavior, and mechanical and thermal properties of pure PET, PET/CF and PET/PMMA-g-CF composites were investigated. The results show that [...] Read more.

Poly(ethylene terephthalate) (PET) composites containing carbon fiber (CF) or polymethyl methacrylate (PMMA)-grafted carbon fiber (PMMA-g-CF) were prepared by melt compounding. The rheology, non-isothermal crystallization behavior, and mechanical and thermal properties of pure PET, PET/CF and PET/PMMA-g-CF composites were investigated. The results show that the addition of CF or PMMA-g-CF significantly increases the storage modulus (G′), loss modulus (G″), and complex viscosity (η*) of the composites at low frequency. The Cole-Cole plots confirm that the surface modification of CF leads to a better interaction between the CF and PET, and then decreases the heterogeneity of the polymeric systems, which is confirmed by the SEM observation on the tensile fracture surface of the composites. Non-isothermal crystallization analysis shows that the CF or PMMA-g-CF could serve as nucleation agent to accelerate the crystallization rate of the composites, and the effect of PMMA-g-CF is stronger than that of CF. The result is further confirmed by the analysis of the crystallization activation energy for all composites calculated by the Flynn-Wall-Ozawa method. Moreover, the tensile and impact strength and the thermal stability of the composites are improved by CF, while the incorporation of PMMA-g-CF further enhances the tensile and impact strength and thermal stability. Full article

(This article belongs to the Special Issue Mechanics of Emerging Polymers with Unprecedented Networks)

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15 pages, 3851 KiB

Open AccessArticle

Thermal Stability of Allyl-Functional Phthalonitriles-Containing Benzoxazine/Bismaleimide Copolymers and Their Improved Mechanical Properties

by Mingzhen Xu, Yangxue Lei, Dengxun Ren, Lin Chen, Kui Li and Xiaobo Liu

Polymers 2018, 10(6), 596; https://doi.org/10.3390/polym10060596 - 29 May 2018

Cited by 40 | Viewed by 5038

Abstract

Copolymerization is the typical method to obtain the high-performance resin composites, due to its universality and regulation performance. It can be employed among various resin matrices with active groups to obtain the desired structures, and subsequently, the outstanding properties. In this work, the [...] Read more.

Copolymerization is the typical method to obtain the high-performance resin composites, due to its universality and regulation performance. It can be employed among various resin matrices with active groups to obtain the desired structures, and subsequently, the outstanding properties. In this work, the copolymerization between the allyl-functional phthalonitrile-containing benzoxazine resin (DABA-Ph) and 4,4′-bis(Maleimidodiphenyl)methane (BMI) were monitored. The interactions among the active groups including allyl moieties, maleimide, benzoxazine rings and nitrile groups were investigated. Differential scanning calorimetry (DSC) and dynamic rheological analysis (DRA) were used to study the curing behaviors and the processing properties. The possible curing processes were proposed and confirmed by Fourier transform infrared spectroscopy (FTIR). Then, glass fiber-reinforced DABA-Ph/BMI composites were designed, and their thermal-mechanical properties were studied. Results indicated that all the composites exhibited outstanding flexural strength, flexural modulus, and high glass-transition temperatures (T_g > 450 °C). The thermal stability of the composites was studied by thermogravimetry (TGA) and evaluated by the integral program decomposition temperature (IPDT). it is believed that the excellent thermal mechanical properties and outstanding T_g as well as good thermal stability would enable the reinforced copolymer-based laminates to be applied in wider fields. Full article

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14 pages, 2880 KiB

Open AccessArticle

Lateral Order and Self-Organized Morphology of Diblock Copolymer Micellar Films

by Jiun-You Liou and Ya-Sen Sun

Polymers 2018, 10(6), 597; https://doi.org/10.3390/polym10060597 - 29 May 2018

Cited by 3 | Viewed by 4396

Abstract

We report the lateral order and self-organized morphology of diblock copolymer polystyrene-block-poly(2-vinylpyridine), P(S-b-2VP), and micelles on silicon substrates (SiO_x/Si). These micellar films were prepared by spin coating from polymer solutions of varied concentration of polymer in toluene [...] Read more.

We report the lateral order and self-organized morphology of diblock copolymer polystyrene-block-poly(2-vinylpyridine), P(S-b-2VP), and micelles on silicon substrates (SiO_x/Si). These micellar films were prepared by spin coating from polymer solutions of varied concentration of polymer in toluene onto SiO_x/Si, and were investigated with grazing-incidence small-angle X-ray scattering (GISAXS) and an atomic force microscope (AFM). With progressively increased surface coverage with increasing concentration, loosely packed spherical micelles, ribbon-like nanostructures, and a second layer of spherical micelles were obtained sequentially. Quantitative analysis and simulations of the micellar packing demonstrates that the spatial ordering of the loosely packed spherical micelles altered from short-range order to hexagonal order when the micellar coverage increased from small to moderate densities of the covered surface. At large densities, anisotropic fusion between spherical micelles caused the ribbon-like nanostructures to have a short-range spatial order; the ordering quality of the second layer was governed by the rugged surface of the underlying layer because the valleys between the ribbon-like nanostructures allowed for further deposition of spherical micelles. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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18 pages, 3212 KiB

Open AccessArticle

Interfacial Properties and Hopping Diffusion of Small Nanoparticle in Polymer/Nanoparticle Composite with Attractive Interaction on Side Group

by Kai-Xin Ren, Xiang-Meng Jia, Gui-Sheng Jiao, Tao Chen, Hu-Jun Qian and Zhong-Yuan Lu

Polymers 2018, 10(6), 598; https://doi.org/10.3390/polym10060598 - 29 May 2018

Cited by 9 | Viewed by 4535

Abstract

The diffusion dynamics of fullerene (C

_{60}

) in unentangled linear atactic polystyrene (PS) and polypropylene (PP) melts and the structure and dynamic properties of polymers in interface area are investigated by performing all-atom molecular dynamics simulations. The comparison of the results in [...] Read more.

The diffusion dynamics of fullerene (C

_{60}

) in unentangled linear atactic polystyrene (PS) and polypropylene (PP) melts and the structure and dynamic properties of polymers in interface area are investigated by performing all-atom molecular dynamics simulations. The comparison of the results in two systems emphasises the influence of local interactions exerted by polymer side group on the diffusion dynamics of the nanoparticle. In the normal diffusive regime at long time scales, the displacement distribution function (DDF) follows a Gaussian distribution in PP system, indicating a normal diffusion of C

_{60}

. However, we observe multiple peaks in the DDF curve for C

_{60}

diffusing in PS melt, which indicates a diffusion mechanism of hopping of C

_{60}

. The attractive interaction between C

_{60}

and phenyl ring side groups are found to be responsible for the observed hopping diffusion. In addition, we find that the C

_{60}

is dynamically coupled with a subsection of a tetramer on PS chain, which has a similar size with C

_{60}

. The phenyl ring on PS chain backbone tends to have a parallel configuration in the vicinity of C

_{60}

surface, therefore neighbouring phenyl rings can form chelation effect on the C

_{60}

surface. Consequently, the rotational dynamics of phenyl ring and the translational diffusion of styrene monomers are found to be slowed down in this interface area. We hope our results can be helpful for understanding of the influence of the local interactions on the nanoparticle diffusion dynamics and interfacial properties in polymer/nanoparticle composites. Full article

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15 pages, 641 KiB

Open AccessArticle

Flow Behavior of Chain and Star Polymers and Their Mixtures

by Deepika Srivastva and Arash Nikoubashman

Polymers 2018, 10(6), 599; https://doi.org/10.3390/polym10060599 - 29 May 2018

Cited by 18 | Viewed by 6880

Abstract

Star-shaped polymers show a continuous change of properties from flexible linear chains to soft colloids, as the number of arms is increased. To investigate the effect of macromolecular architecture on the flow properties, we employ computer simulations of single chain and star polymers [...] Read more.

Star-shaped polymers show a continuous change of properties from flexible linear chains to soft colloids, as the number of arms is increased. To investigate the effect of macromolecular architecture on the flow properties, we employ computer simulations of single chain and star polymers as well as of their mixtures under Poiseuille flow. Hydrodynamic interactions are incorporated through the multi-particle collision dynamics (MPCD) technique, while a bead-spring model is used to describe the polymers. For the ultradilute systems at rest, the polymers are distributed uniformly in the slit channel, with a weak dependence on their number of arms. Once flow is applied, however, we find that the stars migrate much more strongly towards the channel center as the number of arms is increased. In the star-chain mixtures, we find a flow-induced separation between stars and chains, with the stars located in the channel center and the chains closer to the walls. In order to identify the origin of this flow-induced partitioning, we conduct additional simulations without hydrodynamic interactions, and find that the observed cross-stream migration originates from a combination of wall-induced hydrodynamic lift forces and viscoelastic effects. The results from our study give valuable insights for designing microfluidic devices for separating polymers based on their architecture. Full article

(This article belongs to the Special Issue Polymer Dynamics)

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19 pages, 3233 KiB

Open AccessArticle

Synthesis and Characterization of Renewable Polyester Coil Coatings from Biomass-Derived Isosorbide, FDCA, 1,5-Pentanediol, Succinic Acid, and 1,3-Propanediol

by Mónica Lomelí-Rodríguez, José Raúl Corpas-Martínez, Susan Willis, Robert Mulholland and Jose Antonio Lopez-Sanchez

Polymers 2018, 10(6), 600; https://doi.org/10.3390/polym10060600 - 29 May 2018

Cited by 62 | Viewed by 10261

Abstract

Biomass-derived polyester coatings for coil applications have been successfully developed and characterized. The coatings were constituted by carbohydrate-derived monomers, namely 2,5-furan dicarboxylic acid, isosorbide, succinic acid, 1,3-propanediol, and 1,5-pentanediol, the latter having previously been used as a plasticizer rather than a structural building [...] Read more.

Biomass-derived polyester coatings for coil applications have been successfully developed and characterized. The coatings were constituted by carbohydrate-derived monomers, namely 2,5-furan dicarboxylic acid, isosorbide, succinic acid, 1,3-propanediol, and 1,5-pentanediol, the latter having previously been used as a plasticizer rather than a structural building unit. The effect of isosorbide on the coatings is widely studied. The inclusion of these monomers diversified the mechanical properties of the coatings, and showed an improved performance against common petrochemical derived coatings. This research study provides a range of fully bio-derived polyester coil coatings with tunable properties of industrial interest, highlighting the importance of renewable polymers towards a successful bioeconomy. Full article

(This article belongs to the Special Issue Polymers from Renewable Resources)

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13 pages, 3472 KiB

Open AccessArticle

Synthesis and Performances of Phase Change Microcapsules with a Polymer/Diatomite Hybrid Shell for Thermal Energy Storage

by Yanli Sun, Rui Wang, Xing Liu, Erqing Dai, Bo Li, Shu Fang and Danyang Li

Polymers 2018, 10(6), 601; https://doi.org/10.3390/polym10060601 - 30 May 2018

Cited by 18 | Viewed by 4700

Abstract

The mechanical behavior of phase-change microcapsules (microPCMs) is of vital significance for practical applications in thermal energy storage. Hence, a new type of microPCMs based on an n-octadecane (C18) core and a melamine-urea-formaldehyde (MUF)/diatomite hybrid shell was developed through in situ polymerization. Based [...] Read more.

The mechanical behavior of phase-change microcapsules (microPCMs) is of vital significance for practical applications in thermal energy storage. Hence, a new type of microPCMs based on an n-octadecane (C18) core and a melamine-urea-formaldehyde (MUF)/diatomite hybrid shell was developed through in situ polymerization. Based on SEM micrographs, most microPCMs exhibited a nearly spherical and smooth microstructure, with broadened particle size distributions. It was confirmed by Fourier transform infrared (FTIR) that successful polymerization of diatomite into the microPCMs occurred, and that additional diatomite had no effect on the core coated by the shell. In addition, the results of the differential scanning calorimeter (DSC) and Atomic Force Microscopy (AFM) demonstrated that the mechanical properties of the microPCMs were remarkably improved by the addition of a moderate amount of diatomite, but that the heat enthalpy and encapsulated efficiency (η) decreased slightly. The incorporation of 2 wt % diatomite resulted in the average Young’s modulus of microPCMs, which was 1.64 times greater than those of microPCMs without diatomite. Furthermore, the melting and crystallization enthalpies and the encapsulated efficiency of the microPCMs were as high as 237.6 J/g, 234.4 J/g and 77.90%, respectively. The microPCMs with a polymer/diatomite hybrid shell may become the potential materials in the application of thermal energy storage. Full article

(This article belongs to the Special Issue Core-Shell Structured Polymers)

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16 pages, 2186 KiB

Open AccessArticle

Characterization of the Low Molar Ratio Urea–Formaldehyde Resin with ¹³C NMR and ESI–MS: Negative Effects of the Post-Added Urea on the Urea–Formaldehyde Polymers

by Hui Wang, Ming Cao, Taohong Li, Long Yang, Zhigang Duan, Xiaojian Zhou and Guanben Du

Polymers 2018, 10(6), 602; https://doi.org/10.3390/polym10060602 - 31 May 2018

Cited by 53 | Viewed by 9127

Abstract

The structural changes during three-step synthesis of low-molar ratio urea–formaldehyde (UF) resin were tracked by quantitative ¹³C nuclear magnetic resonance (¹³C NMR) analysis and electrospray ionization-mass spectrometry (ESI–MS). Condensations that produced polymers were found to be linked by ether bonds [...] Read more.

The structural changes during three-step synthesis of low-molar ratio urea–formaldehyde (UF) resin were tracked by quantitative ¹³C nuclear magnetic resonance (¹³C NMR) analysis and electrospray ionization-mass spectrometry (ESI–MS). Condensations that produced polymers were found to be linked by ether bonds in addition to hydroxymethylation reactions at the first alkaline stage with a formaldehyde to urea ratio of 2:1. Considerable formation of branched methylene linkages, with the highest content among all the condensed structures, was the key feature of the acidic stage. Notable changes were observed for the chemical structures and molecular masses of the resin components after the formaldehyde to urea molar ratio was lowered to 1.2 by adding post-urea at the final alkaline stage. Specifically, most of the branched hydroxymethyl groups on the polymers were cleaved, resulting in a significant decrease in the branching degree of the polymers. The performance degradation of the UF resin was attributed to this debranching effect and the production of components with low molecular masses. Based on the observations, the curing pattern of low molar ratio UF resin was postulated and branched polymeric formaldehyde catcher bearing urea-reactivity was proposed. Full article

(This article belongs to the Collection Polymeric Adhesives)

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17 pages, 8254 KiB

Open AccessArticle

Electrochromic Devices Based on Poly(2,6-di(9H-carbazol-9-yl)pyridine)-Type Polymer Films and PEDOT-PSS

by Chung-Wen Kuo, Bo-Wei Wu, Jeng-Kuei Chang, Jui-Cheng Chang, Li-Ting Lee, Tzi-Yi Wu and Tsung-Han Ho

Polymers 2018, 10(6), 604; https://doi.org/10.3390/polym10060604 - 31 May 2018

Cited by 20 | Viewed by 4971

Abstract

2,6-Di(9H-carbazol-9-yl)pyridine (DiCP) was synthesized and its corresponding homopolymer (PDiCP) and copolymers (P(DiCP-co-CPDT), P(DiCP-co-CPDT2), P(DiCP-co-CPDTK), and P(DiCP-co-CPDTK2)) were synthesized electrochemically. The anodic copolymer with DiCP:cyclopentadithiophene ketone (CPDTK) = 1:1 feed molar ratio showed high transmittance change [...] Read more.

2,6-Di(9H-carbazol-9-yl)pyridine (DiCP) was synthesized and its corresponding homopolymer (PDiCP) and copolymers (P(DiCP-co-CPDT), P(DiCP-co-CPDT2), P(DiCP-co-CPDTK), and P(DiCP-co-CPDTK2)) were synthesized electrochemically. The anodic copolymer with DiCP:cyclopentadithiophene ketone (CPDTK) = 1:1 feed molar ratio showed high transmittance change (ΔT%) and colouration efficiency (η), which were measured as 39.5% and 184.1 cm² C⁻¹ at 1037 nm, respectively. Electrochromic devices (ECDs) were composed of PDiCP, P(DiCP-co-CPDT), P(DiCP-co-CPDT2), P(DiCP-co-CPDTK), and P(DiCP-co-CPDTK2) as anodically-colouring polymers, and poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT-PSS) as cathodically-colouring polymers. P(DiCP-co-CPDTK)/PEDOT-PSS ECD showed light silverish-yellow at 0.0 V, light grey at 0.7 V, grey at 1.3 V, light greyish blue at 1.7 V, and greyish blue at 2.0 V. Moreover, P(DiCP-co-CPDTK)/PEDOT-PSS ECD presented high ΔT (38.2%) and high η (633.8 cm² C⁻¹) at 635 nm. Full article

(This article belongs to the Special Issue Electrochromic Polymers)

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16 pages, 7212 KiB

Open AccessArticle

Preparation and Characterization of Superabsorbent Polymers Based on Starch Aldehydes and Carboxymethyl Cellulose

by Jungmin Lee, Soohee Park, Hyun-gyoo Roh, Seungtaek Oh, Sunghoon Kim, Myounguk Kim, Donghyun Kim and Jongshin Park

Polymers 2018, 10(6), 605; https://doi.org/10.3390/polym10060605 - 2 Jun 2018

Cited by 56 | Viewed by 12116

Abstract

Superabsorbent polymers (SAPs) are crosslinked hydrophilic polymers that are capable of absorbing large amounts of water. Commercial SAPs are mostly produced with acrylic acid that cannot be easily biodegraded. Therefore, in this study, polysaccharide-based SAPs using carboxymethyl cellulose as a major component were [...] Read more.

Superabsorbent polymers (SAPs) are crosslinked hydrophilic polymers that are capable of absorbing large amounts of water. Commercial SAPs are mostly produced with acrylic acid that cannot be easily biodegraded. Therefore, in this study, polysaccharide-based SAPs using carboxymethyl cellulose as a major component were prepared. Starch aldehydes and citric acid were selected due to their environment-friendly, non-toxic, and biodegradable properties compared to conventional crosslinking agents. Starch aldehydes were prepared by periodate oxidation, which forms aldehyde groups by taking the places of C–OH groups at C-2 and C-3. Furthermore, starch aldehydes were analyzed through the change in FT-IR spectra, the aldehyde quantitation, and the morphology in FE-SEM images. In the crosslinking of polysaccharide-based SAPs, the acetal bridges from starch aldehydes led to a large amount of water entering the network structure of the SAPs. However, the ester bridges from citric acid interfered with the water penetration. In addition, the swelling behavior of the SAPs was analyzed by the Fickian diffusion model and the Schott’s pseudo second order kinetics model. The relationship between swelling behavior and morphology of the SAPs was analyzed by FE-SEM images. In conclusion, polysaccharide-based SAPs were well prepared and the highest equilibrium swelling ratio was 87.0 g/g. Full article

(This article belongs to the Special Issue Polysaccharides)

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16 pages, 8032 KiB

Open AccessArticle

Enduring and Stable Surface Dielectric Barrier Discharge (SDBD) Plasma Using Fluorinated Multi-Layered Polyimide

by Dongliang Bian and Yun Wu

Polymers 2018, 10(6), 606; https://doi.org/10.3390/polym10060606 - 2 Jun 2018

Cited by 6 | Viewed by 5513

Abstract

In this work, multi-layered polyimide (PI) films were surface fluorinated at 328 K and 0.05 MPa using F₂/N₂ mixture with 20% F₂ by volume, for a fluorination time of 0, 30 and 60 min, respectively. Then, they were subjected [...] Read more.

In this work, multi-layered polyimide (PI) films were surface fluorinated at 328 K and 0.05 MPa using F₂/N₂ mixture with 20% F₂ by volume, for a fluorination time of 0, 30 and 60 min, respectively. Then, they were subjected to discharge plasma as barrier dielectrics of surface dielectric barrier discharge (SDBD) at ambient atmospheric air. The dielectric lifetime of SDBD greatly extends after 60 min surface fluorination. In addition, optical emission spectroscopy (OES) results indicate that during the plasma processing, SDBD with fluorinated PI can obtain more stable plasma parameters, including gas temperature and electron temperature. Dielectric surface properties were further evaluated by infrared thermography, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). It is considered that both physical and chemical effects lead to the extension of dielectric lifetime. The physical effect is reflected in low surface temperature and increased surface roughness, while the chemical effect is reflected in the graft of fluorine groups. Full article

(This article belongs to the Special Issue Plasma Processing in Polymers)

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19 pages, 12002 KiB

Open AccessArticle

Preparation, Characterization and Wound Healing Effects of New Membranes Based on Chitosan, Hyaluronic Acid and Arginine Derivatives

by Andreea-Teodora Iacob, Maria Drăgan, Nicolae Ghețu, Dragoș Pieptu, Cornelia Vasile, Frédéric Buron, Sylvain Routier, Simona Elena Giusca, Irina-Draga Caruntu and Lenuța Profire

Polymers 2018, 10(6), 607; https://doi.org/10.3390/polym10060607 - 2 Jun 2018

Cited by 41 | Viewed by 6794

Abstract

New membranes based on chitosan and chitosan-hyaluronic acid containing new arginine derivatives with thiazolidine-4-one scaffold have been prepared using the ionic cross-linking method. The presence of the arginine derivatives with thiazolidine-4-one scaffold into the polymer matrix was proved by Fourier-transform infrared spectroscopy (FT-IR). [...] Read more.

New membranes based on chitosan and chitosan-hyaluronic acid containing new arginine derivatives with thiazolidine-4-one scaffold have been prepared using the ionic cross-linking method. The presence of the arginine derivatives with thiazolidine-4-one scaffold into the polymer matrix was proved by Fourier-transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) revealed a micro-porous structure that is an important characteristic for the treatment of burns, favoring the exudate absorption, the rate of colonization, the cell structure, and the angiogenesis process. The developed polymeric membranes also showed good swelling degree, improved hydrophilicity, and biocompatibility in terms of surface free energy components, which supports their application for tissue regeneration. Moreover, the chitosan-arginine derivatives (CS-6h, CS-6i) and chitosan-hyaluronic acid-arginine derivative (CS-HA-6h) membranes showed good healing effects on the burn wound model induced to rats. For these membranes a complete reepithelialization was observed after 15 days of the experiment, which supports a faster healing process. Full article

(This article belongs to the Collection Polysaccharides)

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18 pages, 7681 KiB

Open AccessArticle

Thermal and Mechanical Properties of Bamboo Fiber Reinforced Epoxy Composites

by Kai Zhang, Fangxin Wang, Wenyan Liang, Zhenqing Wang, Zhiwei Duan and Bin Yang

Polymers 2018, 10(6), 608; https://doi.org/10.3390/polym10060608 - 3 Jun 2018

Cited by 218 | Viewed by 15115

Abstract

Bamboo fibers demonstrate enormous potential as the reinforcement phase in composite materials. In this study, in order to find suitable NaOH concentration for bamboo fiber treatment, bamboo fibers were treated with 2 wt.%, 6 wt.% and 10 wt.% NaOH solutions for 12 h, [...] Read more.

Bamboo fibers demonstrate enormous potential as the reinforcement phase in composite materials. In this study, in order to find suitable NaOH concentration for bamboo fiber treatment, bamboo fibers were treated with 2 wt.%, 6 wt.% and 10 wt.% NaOH solutions for 12 h, respectively. We determined that 6 wt.% NaOH treated bamboo fibers were optimal for the fabrication of bamboo fiber composites by single fiber tensile test, single fiber pull-out test, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The short length bamboo fibers treated with 6 wt.% NaOH solutions were well dispersed in the epoxy matrix by a new preparation method. The effect of fiber content and fiber length on the mechanical behavior of bamboo fiber reinforced epoxy composites was investigated. The results confirmed that fracture toughness and flexural modulus of the composites monotonically increased with fiber length and content. However, for all samples, composites showed negligible difference on the flexural strength. The fracture surfaces of the composites were observed by SEM, revealing that fiber breakage, matrix cracking, debonding, and fiber pull out were major failure types. In addition, thermogravimetric analysis (TGA) was carried out to investigate the thermal behavior of both bamboo fibers and composites. Full article

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8 pages, 2605 KiB

Open AccessArticle

Electrospun PVA Polymer Embedded with Ceria Nanoparticles as Silicon Solar Cells Rear Surface Coaters for Efficiency Improvement

by Effat Samir, Mohamed Salah, Ali Hajjiah, Nader Shehata, Marwa Fathy and Aya Hamed

Polymers 2018, 10(6), 609; https://doi.org/10.3390/polym10060609 - 4 Jun 2018

Cited by 10 | Viewed by 4010

Abstract

This paper introduces electrospun nanofibers embedded with ceria nanoparticles as silicon solar cells coaters, showing their influence on the solar cells efficiency. Ceria nanoparticles can be synthesized to have formed oxygen vacancies (O-vacancies), which are associated with converting cerium ions from the Ce [...] Read more.

This paper introduces electrospun nanofibers embedded with ceria nanoparticles as silicon solar cells coaters, showing their influence on the solar cells efficiency. Ceria nanoparticles can be synthesized to have formed oxygen vacancies (O-vacancies), which are associated with converting cerium ions from the Ce⁴⁺ state ions to the Ce³⁺ ones. These O-vacancies follow the rule of improving silicon solar cellconductivity through the hopping mechanism. Besides, under violet excitation, the reduced trivalent cerium Ce³⁺ ions are directly responsible for down-converting the un-absorbed violet or ultra-violet (UV) wavelengths to a resulted green fluorescence emission at ~520 nm. These are absorbed through the silicon solar cells active layer. When electrospun Poly(vinyl alcohol) (PVA) is embedded with ceria nanoparticles on the rear surface of silicon solar cell, a promising enhancement in the behavior of solar cells current–voltage (I–V) curve is observed. The efficiency has improved by about 24% of its initial value due to the mutual impact of improving both electrical conductivity and optical conversions from the higher surface-to-volume ratio of electrospun nanofibers embedded by ceria nanoparticles. The solar cell efficiency improvement is due to the mutual impact of both optical down-conversion and better electric paths via the used nanocomposite. The added nanostructures coating can utilize part of the transmitted UV or violet spectrum through the cell as optical conversion from violet to the visible region. In addition, the formed active tri-valent states are associated with O-vacancies which can help in a better conductivity of the generated photoelectrons from the cell through the hopping mechanism. The PVA nanofibers host offers a better distribution of ceria nanoparticles and better conductivity paths for the photoelectrons based on the better surface-to-volume ratio of the nanofibers. Full article

(This article belongs to the Special Issue Polymer Hybrid Materials)

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11 pages, 2684 KiB

Open AccessArticle

Highly Graphitized Carbon Coating on SiO with a π–π Stacking Precursor Polymer for High Performance Lithium-Ion Batteries

by Shan Fang, Ning Li, Tianyue Zheng, Yanbao Fu, Xiangyun Song, Ting Zhang, Shaopeng Li, Bin Wang, Xiaogang Zhang and Gao Liu

Polymers 2018, 10(6), 610; https://doi.org/10.3390/polym10060610 - 4 Jun 2018

Cited by 17 | Viewed by 6878

Abstract

A highly graphitized carbon on a silicon monoxide (SiO) surface coating at low temperature, based on polymer precursor π–π stacking, was developed. A novel conductive and electrochemically stable carbon coating was rationally designed to modify the SiO anode materials by controlling the sintering [...] Read more.

A highly graphitized carbon on a silicon monoxide (SiO) surface coating at low temperature, based on polymer precursor π–π stacking, was developed. A novel conductive and electrochemically stable carbon coating was rationally designed to modify the SiO anode materials by controlling the sintering of a conductive polymer, a pyrene-based homopolymer poly (1-pyrenemethyl methacrylate; PPy), which achieved high graphitization of the carbon layers at a low temperature and avoided silicon carbide formation and possible SiO material transformation. When evaluated as the anode of a lithium-ion battery (LIB), the carbon-coated SiO composite delivered a high discharge capacity of 2058.6 mAh/g at 0.05 C of the first formation cycle with an initial Coulombic efficiency (ICE) of 62.2%. After 50 cycles at 0.1 C, this electrode capacity was 1090.2 mAh/g (~82% capacity retention, relative to the capacity of the second cycle at 0.1 °C rate), and a specific capacity of 514.7 mAh/g was attained at 0.3 C after 500 cycles. Furthermore, the coin-type full cell composed of the carbon coated SiO composite anode and the Li[Ni_0.5Co_0.2Mn_0.3O₂] cathode attained excellent cycling performance. The results show the potential applications for using a π–π stacking polymer precursor to generate a highly graphitize coating for next-generation high-energy-density LIBs. Full article

(This article belongs to the Special Issue π-Stacked Polymers)

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9 pages, 4241 KiB

Open AccessCommunication

Synthetic Glycopolypeptide Micelle for Targeted Drug Delivery to Hepatic Carcinoma

by Pengqiang Li, Jiandong Han, Di Li, Jinjin Chen, Wei Wang and Weiguo Xu

Polymers 2018, 10(6), 611; https://doi.org/10.3390/polym10060611 - 4 Jun 2018

Cited by 11 | Viewed by 4090

Abstract

The targeted delivery of chemotherapy drugs to tumor lesions is a major challenge for the treatment of tumors. Up until now, various polymeric nanoparticles have been explored to improve the targetability of these therapeutic drugs through passive or active targeting processes. In the [...] Read more.

The targeted delivery of chemotherapy drugs to tumor lesions is a major challenge for the treatment of tumors. Up until now, various polymeric nanoparticles have been explored to improve the targetability of these therapeutic drugs through passive or active targeting processes. In the design and construction of polymer nanoparticles, glycopolypeptide has shown great potential owing to its excellent targeting ability and biocompatibility. In order to enhance the antitumor effect of doxorubicin (DOX), a glycopolypeptide-based micelle (GPM) modified by α-lactose (Lac) was synthesized for targeted treatment of hepatoma. The DOX-loaded GPM (i.e., GPM/DOX) could significantly target human hepatoma (HepG2) cells and further inhibit their proliferation in vitro. Additionally, GPM/DOX exhibited a much higher drug accumulation in tumor tissue and a stronger antitumor effect in vivo than free DOX. The above results revealed that this drug delivery system provides a promising platform for the targeting therapy of hepatic cancer. Full article

(This article belongs to the Special Issue Smart Polymers)

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11 pages, 1631 KiB

Open AccessArticle

Chirality Construction from Preferred π-π Stacks of Achiral Azobenzene Units in Polymer: Chiral Induction, Transfer and Memory

by Tengfei Miao, Lu Yin, Xiaoxiao Cheng, Yin Zhao, Wenjie Hou, Wei Zhang and Xiulin Zhu

Polymers 2018, 10(6), 612; https://doi.org/10.3390/polym10060612 - 4 Jun 2018

Cited by 23 | Viewed by 5382

Abstract

The induction of supramolecular chirality from achiral polymers has been widely investigated in composite systems consisting of a chiral guest, achiral host, and solvents. To further study and understand the process of chirality transfer from a chiral solvent or chiral molecules to an [...] Read more.

The induction of supramolecular chirality from achiral polymers has been widely investigated in composite systems consisting of a chiral guest, achiral host, and solvents. To further study and understand the process of chirality transfer from a chiral solvent or chiral molecules to an achiral polymer backbone or side-chain units, an alternative is to reduce the components in the supramolecular assembled systems. Herein, achiral side-chain azobenzene (Azo)-containing polymers, poly(6-[4-(4-methoxyphenylazo) phenoxy] hexyl methacrylate) (PAzoMA), with different M_ns, were synthesized by atom transfer radical polymerization (ATRP). Preferred chirality from supramolecular assembled trans-Azo units of PAzoMAs is successfully induced solely by the neat limonene. These aggregates of the polymers in limonene solution were characterized by circular dichroism (CD), UV-vis spectra, and dynamic light scattering (DLS) under different temperatures. The temperature plays an important role in the course of chiral induction. Meanwhile, supramolecular chirality can be constructed in the solid films of the achiral side-chain Azo-containing polymers that were triggered by limonene vapors. Also, it can be erased after heated above the glass transition temperature (T_g) of the polymer, and recovered after cooling down in the limonene vapors. A chiroptical switch can be built by alternately changing the temperature. The solid films show good chiral memory behaviors. The current results will facilitate studying the mechanism of chirality transfer induced by chiral solvent and improve potential application possibilities in chiral film materials. Full article

(This article belongs to the Special Issue π-Stacked Polymers)

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14 pages, 3428 KiB

Open AccessArticle

Effects of Modified Graphene Oxide on Thermal and Crystallization Properties of PET

by Li Xing, Yao Wang, Shichao Wang, Yu Zhang, Sui Mao, Guanghui Wang, Jixian Liu, Linjun Huang, Hao Li, Laurence A. Belfiore and Jianguo Tang

Polymers 2018, 10(6), 613; https://doi.org/10.3390/polym10060613 - 4 Jun 2018

Cited by 37 | Viewed by 6680

Abstract

In this article, graphene oxide nanosheets grafted with low molecular weight poly(ethylene terephthalate) were in situ synthesized via carboxylation, acyl chlorination and grafting modification in order to improve the compatibility between GO and PET phases and enhance the thermal stability and crystallization properties [...] Read more.

In this article, graphene oxide nanosheets grafted with low molecular weight poly(ethylene terephthalate) were in situ synthesized via carboxylation, acyl chlorination and grafting modification in order to improve the compatibility between GO and PET phases and enhance the thermal stability and crystallization properties of PET. Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Atomic Force Microscopy (AFM) characterization results demonstrated that LMPET chains have been successfully grafted onto the surface of GO. To further investigate the influence of modified GO on properties of PET, modified PET was prepared by incorporating the GL-g-LMPET nanofillers into the PET matrix using the melt-blending method. Due to the similar polarity and strong interaction between LMPET and PET molecules, GL-g-LMPET nanofillers were homogeneously dispersed in PET matrix. Thermal properties and crystallization properties of obtained nanocomposites were systematically characterized using Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Thermo Gravimetric Analysis (TGA). Results show that GL-g-LMPET nanofillers could improve the thermal stability of PET, e.g., increase up to 16.6 °C in temperature at the maximum rate of weight loss. In addition, the GL-g-LMPET also acts as an efficient nucleating agent for PET, exhibiting (1) higher crystallization temperatures; (2) higher degrees of crystallinity; and (3) faster rates of crystallization. Full article

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13 pages, 3203 KiB

Open AccessArticle

Preparation and Characterization of Regenerated Cellulose Film from a Solution in Lithium Bromide Molten Salt Hydrate

by Xueqin Zhang, Naiyu Xiao, Huihui Wang, Chuanfu Liu and Xuejun Pan

Polymers 2018, 10(6), 614; https://doi.org/10.3390/polym10060614 - 4 Jun 2018

Cited by 76 | Viewed by 8545

Abstract

In this study, the molten salt hydrate of lithium bromide (LiBr) was utilized as a non-derivatizing cellulose dissolution solvent to prepare regenerated cellulose films for kraft pulp. The effects of LiBr concentrations (60, 62, and 65 wt %) and dissolving time (from 5 [...] Read more.

In this study, the molten salt hydrate of lithium bromide (LiBr) was utilized as a non-derivatizing cellulose dissolution solvent to prepare regenerated cellulose films for kraft pulp. The effects of LiBr concentrations (60, 62, and 65 wt %) and dissolving time (from 5 to 40 min with the interval of 5 min) on the structures and the properties of the films were investigated. Fourier transform infrared (FT-IR) and cross-polarization magic-angle spinning carbon-13 nuclear magnetic resonance (CP/MAS ¹³C NMR) characterizations verified the breakage of inter- and intra-cellulose hydrogen bonds during the regeneration, resulting in the disruption of the crystalline structure of cellulose. X-ray diffraction (XRD) data indicated that the regeneration converted the polymorphism of cellulose from I to II as well as decreased its crystallinity. Ultraviolet-visible spectra (UV-Vis) and scanning electron microscopy (SEM) analyses revealed the excellent optical transparency of the films to visible light due to the complete dissolution of cellulose fibers as well as the sufficient breaking of the inter- and intra-cellulose hydrogen bonds. In terms of tensile testing, tuning LiBr concentrations and dissolving time could increase the elongation at break and tensile strength of the films. The maximum elongation at break of 26% and tensile strength of 67 MPa were achieved when the films prepared in 65 wt % LiBr for 10 and 15 min, respectively. These results indicated the great potential of the cellulose films for packaging use. Full article

(This article belongs to the Collection Polysaccharides)

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20 pages, 1946 KiB

Open AccessArticle

Modulation of the Catalytic Properties of Lipase B from Candida antarctica by Immobilization on Tailor-Made Magnetic Iron Oxide Nanoparticles: The Key Role of Nanocarrier Surface Engineering

by Mario Viñambres, Marco Filice and Marzia Marciello

Polymers 2018, 10(6), 615; https://doi.org/10.3390/polym10060615 - 5 Jun 2018

Cited by 18 | Viewed by 5574

Abstract

The immobilization of biocatalysts on magnetic nanomaterial surface is a very attractive alternative to achieve enzyme nanoderivatives with highly improved properties. The combination between the careful tailoring of nanocarrier surfaces and the site-specific chemical modification of biomacromolecules is a crucial parameter to finely [...] Read more.

The immobilization of biocatalysts on magnetic nanomaterial surface is a very attractive alternative to achieve enzyme nanoderivatives with highly improved properties. The combination between the careful tailoring of nanocarrier surfaces and the site-specific chemical modification of biomacromolecules is a crucial parameter to finely modulate the catalytic behavior of the biocatalyst. In this work, a useful strategy to immobilize chemically aminated lipase B from Candida antarctica on magnetic iron oxide nanoparticles (IONPs) by covalent multipoint attachment or hydrophobic physical adsorption upon previous tailored engineering of nanocarriers with poly-carboxylic groups (citric acid or succinic anhydride, CALB_EDA@CA-NPs and CALB_EDA@SA-NPs respectively) or hydrophobic layer (oleic acid, CALB_EDA@OA-NPs) is described. After full characterization, the nanocatalysts have been assessed in the enantioselective kinetic resolution of racemic methyl mandelate. Depending on the immobilization strategy, each enzymatic nanoderivative permitted to selectively improve a specific property of the biocatalyst. In general, all the immobilization protocols permitted loading from good to high lipase amount (149 < immobilized lipase < 234 mg/g_Fe). The hydrophobic CALB_EDA@OA-NPs was the most active nanocatalyst, whereas the covalent CALB_EDA@CA-NPs and CALB_EDA@SA-NPs were revealed to be the most thermostable and also the most enantioselective ones in the kinetic resolution reaction (almost 90% ee R-enantiomer). A strategy to maintain all these properties in long-time storage (up to 1 month) by freeze-drying was also optimized. Therefore, the nanocarrier surface engineering is demonstrated to be a key-parameter in the design and preparation of lipase libraries with enhanced catalytic properties. Full article

(This article belongs to the Special Issue Selected Papers from "ECIS 2017")

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13 pages, 2045 KiB

Open AccessArticle

Structural and Thermoanalytical Characterization of 3D Porous PDMS Foam Materials: The Effect of Impurities Derived from a Sugar Templating Process

by José González-Rivera, Rossella Iglio, Giuseppe Barillaro, Celia Duce and Maria Rosaria Tinè

Polymers 2018, 10(6), 616; https://doi.org/10.3390/polym10060616 - 5 Jun 2018

Cited by 87 | Viewed by 14111

Abstract

Polydimethylsiloxane (PDMS) polymers are extensively used in a wide range of research and industrial fields, due to their highly versatile chemical, physical, and biological properties. Besides the different two-dimensional PDMS formulations available, three-dimensional PDMS foams have attracted increased attention. However, as-prepared PDMS foams [...] Read more.

Polydimethylsiloxane (PDMS) polymers are extensively used in a wide range of research and industrial fields, due to their highly versatile chemical, physical, and biological properties. Besides the different two-dimensional PDMS formulations available, three-dimensional PDMS foams have attracted increased attention. However, as-prepared PDMS foams contain residual unreacted low molecular weight species that need to be removed in order to obtain a standard and chemically stable material for use as a scaffold for different decorating agents. We propose a cleaning procedure for PDMS foams obtained using a sugar templating process, based on the use of two different solvents (hexane and ethanol) as cleaning agents. Thermogravimetry coupled with Fourier Transform Infrared Spectroscopy (TG-FTIR) for the analysis of the evolved gasses was used to characterize the thermal stability and decomposition pathway of the PDMS foams, before and after the cleaning procedure. The results were compared with those obtained on non-porous PDMS bulk as a reference. Micro-CT microtomography and scanning electron microscopy (SEM) analyses were employed to study the morphology of the PDMS foam. The thermogravimetric analysis (TGA) revealed a different thermal behaviour and crosslinking pathway between bulk PDMS and porous PDMS foam, which was also influenced by the washing process. This information was not apparent from spectroscopic or morphological studies and it would be very useful for planning the use of such complex and very reactive systems. Full article

(This article belongs to the Special Issue Siloxane-Based Polymers)

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13 pages, 6957 KiB

Open AccessArticle

Gluten Polymer Networks—A Microstructural Classification in Complex Systems

by Isabelle Lucas, Thomas Becker and Mario Jekle

Polymers 2018, 10(6), 617; https://doi.org/10.3390/polym10060617 - 5 Jun 2018

Cited by 33 | Viewed by 7280

Abstract

A classification of gluten polymer networks would support a better understanding of structure-function relationships of any gluten polymer material and thus, the control of processing properties. However, quantification and interpretation of the gluten network structures is challenging due to their complexity. Thus, the [...] Read more.

A classification of gluten polymer networks would support a better understanding of structure-function relationships of any gluten polymer material and thus, the control of processing properties. However, quantification and interpretation of the gluten network structures is challenging due to their complexity. Thus, the network formation was altered by specific gluten-modifying agents (glutathione, ascorbic acid, potassium bromate, glucose oxidase, transglutaminase, bromelain) in this study in order to clarify if structural alterations can be detected on a microstructural level and to specify different polymer arrangements in general. Microstructure analysis was performed by confocal laser scanning microscopy followed by quantification with protein network analysis. It was shown that alterations in gluten microstructure could be elucidated according to the kind of modification in cross-linking (disulphide, (iso) peptide, dityrosyl). Linear correlations of structural network attributes among each other were found, leading to an assertion in general: the higher the branching rate, the thinner the protein threads and the larger the interconnected protein aggregate. Considering the morphological attribute lacunarity, a quantitative classification of different gluten arrangements was established. These assertions were extended by using unspecific gluten-modifying agents in addition to the specific ones. Ultimately, five network types were proposed based on diverse polymer arrangements. Full article

(This article belongs to the Special Issue Protein Biopolymer)

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16 pages, 4976 KiB

Open AccessArticle

Effect of the Polyketone Aromatic Pendent Groups on the Electrical Conductivity of the Derived MWCNTs-Based Nanocomposites

by Nicola Migliore, Lorenzo Massimo Polgar, Rodrigo Araya-Hermosilla, Francesco Picchioni, Patrizio Raffa and Andrea Pucci

Polymers 2018, 10(6), 618; https://doi.org/10.3390/polym10060618 - 5 Jun 2018

Cited by 17 | Viewed by 6193

Abstract

Electrically conductive plastics with a stable electric response within a wide temperature range are promising substitutes of conventional inorganic conductive materials. This study examines the preparation of thermoplastic polyketones (PK30) functionalized by the Paal–Knorr process with phenyl (PEA), thiophene (TMA), and pyrene (PMA) [...] Read more.

Electrically conductive plastics with a stable electric response within a wide temperature range are promising substitutes of conventional inorganic conductive materials. This study examines the preparation of thermoplastic polyketones (PK30) functionalized by the Paal–Knorr process with phenyl (PEA), thiophene (TMA), and pyrene (PMA) pendent groups with the aim of optimizing the non-covalent functionalization of multiwalled carbon nanotubes (MWCNTs) through π–π interactions. Among all the aromatic functionalities grafted to the PK30 backbone, the extended aromatic nuclei of PMA were found to be particularly effective in preparing well exfoliated and undamaged MWCNTs dispersions with a well-defined conductive percolative network above the 2 wt % of loading and in freshly prepared nanocomposites as well. The efficient and superior π–π interactions between PK30PMA and MWCNTs consistently supported the formation of nanocomposites with a highly stable electrical response after thermal solicitations such as temperature annealing at the softening point, IR radiation exposure, as well as several heating/cooling cycles from room temperature to 75 °C. Full article

(This article belongs to the Special Issue Smart and Modern Thermoplastic Polymer Materials)

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15 pages, 3101 KiB

Open AccessArticle

Acetyl Groups in Typha capensis: Fate of Acetates during Organosolv and Ionosolv Pulping

by Idi Guga Audu, Nicolas Brosse, Heiko Winter, Anton Hoffmann, Martina Bremer, Steffen Fischer and Marie-Pierre Laborie

Polymers 2018, 10(6), 619; https://doi.org/10.3390/polym10060619 - 5 Jun 2018

Cited by 8 | Viewed by 5784

Abstract

During biomass fractionation, any native acetylation of lignin and heteropolysaccharide may affect the process and the resulting lignin structure. In this study, Typha capensis (TC) and its lignin isolated by milling (MWL), ionosolv (ILL) and organosolv (EOL) methods were investigated for acetyl group [...] Read more.

During biomass fractionation, any native acetylation of lignin and heteropolysaccharide may affect the process and the resulting lignin structure. In this study, Typha capensis (TC) and its lignin isolated by milling (MWL), ionosolv (ILL) and organosolv (EOL) methods were investigated for acetyl group content using FT-Raman, ¹H NMR, 2D-NMR, back-titration, and Zemplén transesterification analytical methods. The study revealed that TC is a highly acetylated grass; extractive free TC (TC_extr) and TC MWL exhibited similar values of acetyl content: 6 wt % and 8 wt % by Zemplén transesterification, respectively, and 11 wt % by back-titration. In contrast, lignin extracted from organosolv and [EMIm][OAc] pulping lost 80% of the original acetyl groups. With a high acetyl content in the natural state, TC could be an interesting raw material in biorefinery in which acetic acid could become an important by-product. Full article

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27 pages, 4215 KiB

Open AccessArticle

Gelatin/Nanohyroxyapatite Cryogel Embedded Poly(lactic-co-glycolic Acid)/Nanohydroxyapatite Microsphere Hybrid Scaffolds for Simultaneous Bone Regeneration and Load-Bearing

by K. T. Shalumon, Chang-Yi Kuo, Chak-Bor Wong, Yen-Miao Chien, Huai-An Chen and Jyh-Ping Chen

Polymers 2018, 10(6), 620; https://doi.org/10.3390/polym10060620 - 5 Jun 2018

Cited by 35 | Viewed by 7405

Abstract

It is desirable to combine load-bearing and bone regeneration capabilities in a single bone tissue engineering scaffold. For this purpose, we developed a high strength hybrid scaffold using a sintered poly(lactic-co-glycolic acid) (PLGA)/nanohydroxyapatite (nHAP) microsphere cavity fitted with gelatin/nHAP cryogel disks [...] Read more.

It is desirable to combine load-bearing and bone regeneration capabilities in a single bone tissue engineering scaffold. For this purpose, we developed a high strength hybrid scaffold using a sintered poly(lactic-co-glycolic acid) (PLGA)/nanohydroxyapatite (nHAP) microsphere cavity fitted with gelatin/nHAP cryogel disks in the center. Osteo-conductive/osteo-inductive nHAP was incorporated in 250–500 μm PLGA microspheres at 40% (w/w) as the base matrix for the high strength cavity-shaped microsphere scaffold, while 20% (w/w) nHAP was incorporated into gelatin cryogels as an embedded core for bone regeneration purposes. The physico-chemical properties of the microsphere, cryogel, and hybrid scaffolds were characterized in detail. The ultimate stress and Young’s modulus of the hybrid scaffold showed 25- and 21-fold increases from the cryogel scaffold. In vitro studies using rabbit bone marrow-derived stem cells (rBMSCs) in cryogel and hybrid scaffolds through DNA content, alkaline phosphatase activity, and mineral deposition by SEM/EDS, showed the prominence of both scaffolds in cell proliferation and osteogenic differentiation of rBMSCs in a normal medium. Calcium contents analysis, immunofluorescent staining of collagen I (COL I), and osteocalcin (OCN) and relative mRNA expression of COL I, OCN and osteopontin (OPN) confirmed in vitro differentiation of rBMSCs in the hybrid scaffold toward the bone lineage. From compression testing, the cell/hybrid scaffold construct showed a 1.93 times increase of Young’s modulus from day 14 to day 28, due to mineral deposition. The relative mRNA expression of osteogenic marker genes COL I, OCN, and OPN showed 5.5, 18.7, and 7.2 folds increase from day 14 to day 28, respectively, confirming bone regeneration. From animal studies, the rBMSCs-seeded hybrid constructs could repair mid-diaphyseal tibia defects in rabbits, as evaluated by micro-computed tomography (μ-CT) and histological analyses. The hybrid scaffold will be useful for bone regeneration in load-bearing areas. Full article

(This article belongs to the Special Issue Polymer Scaffolds for Biomedical Application)

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13 pages, 1953 KiB

Open AccessArticle

Model Studies on Load-Settlement Characteristics of Coarse-Grained Soil Treated with Geofiber and Cement

by Yan Li, Lei Su, Xianzhang Ling, Jiahui Wang and Yingzi Yang

Polymers 2018, 10(6), 621; https://doi.org/10.3390/polym10060621 - 5 Jun 2018

Cited by 8 | Viewed by 4151

Abstract

This study aims to verify the effectiveness of fiber reinforcing with and without cement on settlement controlling of subgrade models, and to investigate the effect of fiber reinforcement on the load-settlement behavior of subgrade models. To this end, laboratory subgrade model tests were [...] Read more.

This study aims to verify the effectiveness of fiber reinforcing with and without cement on settlement controlling of subgrade models, and to investigate the effect of fiber reinforcement on the load-settlement behavior of subgrade models. To this end, laboratory subgrade model tests were conducted under different static vertical loads. Three subgrade models composed of different fillers were constructed in a rigid concrete tank, and the internal earth pressures and settlements at different depths were measured through an earth pressure cell and settlement plate. Results show that the fiber-reinforced model keeps a slight difference to the unreinforced model in terms of earth pressure distribution under lower applied surface pressure. However, the earth pressure at various locations under each surface pressure was obviously lower than that of the other two models due to the combined effect of fiber and cement. In addition, for the unreinforced subgrade model, the 60 cm settlement domain was restricted within 40 cm depth through fiber-cement and fiber reinforcing, and the total settlement under 100 kPa was decreased by 48.5% and 30.8%, respectively. Moreover, reinforced models present with different settlement deformation features. The inflection points, after which the rate of settlement decreased with increasing applied surface pressure, were observed in the pressure-settlement curves. Under 200 kPa, the fiber-cement and fiber reinforcement decreased the total settlement of the unreinforced model by 61.4% and 34.7%, respectively. The greater applied surface pressure, the more efficient was fiber-cement reinforcing in settlement controlling. Full article

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14 pages, 3864 KiB

Open AccessArticle

Metal(II) Coordination Polymers Derived from Mixed 4-Imidazole Ligands and Carboxylates: Syntheses, Topological Structures, and Properties

by Wei-Dong Li, Jia-Le Li, Xing-Zhe Guo, Zhi-You Zhang and Shui-Sheng Chen

Polymers 2018, 10(6), 622; https://doi.org/10.3390/polym10060622 - 6 Jun 2018

Cited by 11 | Viewed by 4841

Abstract

Four new metal–organic coordination polymers [Cu(L)(mpa)]·3H₂O (1), [Co(L)(mpa)]·H₂O (2), [Zn(L)(mpa)]·H₂O (3), and [Cd(L)(mpa)(H₂O)]·H₂O (4) were synthesized by reactions of the corresponding metal(II) salts based on [...] Read more.

Four new metal–organic coordination polymers [Cu(L)(mpa)]·3H₂O (1), [Co(L)(mpa)]·H₂O (2), [Zn(L)(mpa)]·H₂O (3), and [Cd(L)(mpa)(H₂O)]·H₂O (4) were synthesized by reactions of the corresponding metal(II) salts based on mixed ligands of 1,4-di(1H-imidazol-4-yl)benzene (L) and 4-methylphthalic acid (H₂mpa), respectively. The structures of the complexes were characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction. Compound 1 exhibits a binodal 4-connected three dimensional (3D) architecture with (6⁵·8)-CdSO₄ topology, while complexes 2 and 3 are isostructural and have two-dimensional (2D) layer structure with (4, 4) sql topology based on the binuclear metal subunits. Complex 4 has the same 2D layer structure with (4, 4) sql topology as complexes 2 and 3, but the inclined interpenetration of parallel sets of layers result in the formation with 2D + 2D → 3D framework. The activated sample 1 shows selective CO₂ uptake over N₂. The photoluminiscent properties together with quantum yield (QY) and luminescence lifetime are also investigated for complexes 3 and 4 in the solid state at room temperature. Full article

(This article belongs to the Special Issue Advances in Coordination Polymers)

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15 pages, 2863 KiB

Open AccessArticle

Surface Instability of Bilayer Hydrogel Subjected to Both Compression and Solvent Absorption

by Zhiheng Zhou, Ying Li, Tian Fu Guo, Xu Guo and Shan Tang

Polymers 2018, 10(6), 624; https://doi.org/10.3390/polym10060624 - 6 Jun 2018

Cited by 7 | Viewed by 4133

Abstract

The bilayered structure of hard thin film on soft substrate can lose stability and form specific patterns, such as wrinkles or creases, on the surface, induced by external stimuli. For bilayer hydrogels, the surface morphology caused by the instability is usually controlled by [...] Read more.

The bilayered structure of hard thin film on soft substrate can lose stability and form specific patterns, such as wrinkles or creases, on the surface, induced by external stimuli. For bilayer hydrogels, the surface morphology caused by the instability is usually controlled by the solvent-induced swelling/shrinking and mechanical force. Here, two important issues on the instability of bilayer hydrogels, which were not considered in the previous studies, are focused on in this study. First, the upper layer of a hydrogel is not necessarily too thin. Thus we investigated how the thickness of the upper layer can affect the surface morphology of bilayer hydrogels under compression through both finite element (FE) simulation and theoretical analysis. Second, a hydrogel can absorb water molecules before the mechanical compression. The effect of the pre-absorption of water before the mechanical compression was studied through FE simulations and theoretical analysis. Our results show that when the thickness of the upper layer is very large, surface wrinkles can exist without transforming into period doublings. The pre-absorption of the water can result in folds or unexpected hierarchical wrinkles, which can be realized in experiments through further efforts. Full article

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13 pages, 12853 KiB

Open AccessArticle

Highly Efficient Flame Retardant Hybrid Composites Based on Calcium Alginate/Nano-Calcium Borate

by Zhenhui Liu, Zichao Li, Xihui Zhao, Lei Zhang and Qun Li

Polymers 2018, 10(6), 625; https://doi.org/10.3390/polym10060625 - 6 Jun 2018

Cited by 32 | Viewed by 5222

Abstract

Hybrid composites with low flammability based on renewable calcium alginate and nano-calcium borate were fabricated using an in situ method through a simple, eco-friendly vacuum drying process. The composites were characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrum (FTIR), scanning electron microscopy [...] Read more.

Hybrid composites with low flammability based on renewable calcium alginate and nano-calcium borate were fabricated using an in situ method through a simple, eco-friendly vacuum drying process. The composites were characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrum (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The combustion behavior and flammability of the composites were assessed by using the limiting oxygen index (LOI) and cone calorimetry (CONE) tests. The composites showed excellent thermal stability and achieved nonflammability with an LOI higher than 60. Pyrolysis was investigated using pyrolysis–gas chromatography–mass spectrometry (Py-GC-MS) and the results showed that fewer sorts of cracking products were produced from the hybrid composites compared with the calcium alginate. A possible thermal degradation mechanism of composites was proposed based on the experimental data. The combined results indicate that the calcium borate had a nano-effect, accumulating more freely in the hybrid composites and contributing significantly to both the solid phase and gas phase, resulting in an efficient improvement in the flame retardancy of the composites. Our study provides a novel material with promising potentiality for flame retardant applications. Full article

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14 pages, 4401 KiB

Open AccessArticle

Selective and Efficient Arsenic Recovery from Water through Quaternary Amino-Functionalized Silica

by Oscar Valdés, Adolfo Marican, Yaneris Mirabal-Gallardo and Leonardo S. Santos

Polymers 2018, 10(6), 626; https://doi.org/10.3390/polym10060626 - 7 Jun 2018

Cited by 8 | Viewed by 4287

Abstract

The free-radical graft polymerization of acryloxyethyl-trimethylammonium chloride onto commercial silica particles was studied experimentally for extraction of arsenic ions from water. Two steps were used to graft acryloxyethyl-trimethylammonium chloride (Q) onto the surface of nanosilica: anchoring vinyltrimethoxysilane (VTMSO) onto the surface of silica [...] Read more.

The free-radical graft polymerization of acryloxyethyl-trimethylammonium chloride onto commercial silica particles was studied experimentally for extraction of arsenic ions from water. Two steps were used to graft acryloxyethyl-trimethylammonium chloride (Q) onto the surface of nanosilica: anchoring vinyltrimethoxysilane (VTMSO) onto the surface of silica to modify it with double bonds and then grafting Q onto the surface of silica with potassium persulfate as an initiator. The products were characterized by Fourier-transform infrared (FT-IR), the thermogravimetric analysis (TGA), scanning electron microscopy (SEM), ¹³C, ²⁹Si nuclear magnetic resonance (NMR), and X-ray powder diffraction (XRD). The results showed that it is easy to graft Q onto the surface of silica under radical polimerization. The morphology analysis of silica and modified silica indicated that the silica decreased the size scale after modification. Q/VTMSO-SiO₂ was tested for its ability to remove arsenic from drinking water. The results show that the new silica hybrid particles efficiently remove all arsenate ions. In addition, Q/VTMSO-SiO₂ showed better sorption capacities for other metal ions (such as copper, zinc, chromium, uranium, vanadium, and lead) than a commercial water filter. Full article

(This article belongs to the Special Issue Polymers: Design, Function and Application)

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17 pages, 11055 KiB

Open AccessArticle

Water Absorption and Distribution in a Pultruded Unidirectional Carbon/Glass Hybrid Rod under Hydraulic Pressure and Elevated Temperatures

by Chenggao Li, Guijun Xian and Hui Li

Polymers 2018, 10(6), 627; https://doi.org/10.3390/polym10060627 - 7 Jun 2018

Cited by 41 | Viewed by 5174

Abstract

A pultruded unidirectional carbon/glass reinforced epoxy hybrid FRP rod with 19 mm of diameter was developed for a sucker rod and lifting oil wells. The rod possesses a 12-mm diameter carbon fiber core and a 3.5-mm thick outer shell. The rod was exposed [...] Read more.

A pultruded unidirectional carbon/glass reinforced epoxy hybrid FRP rod with 19 mm of diameter was developed for a sucker rod and lifting oil wells. The rod possesses a 12-mm diameter carbon fiber core and a 3.5-mm thick outer shell. The rod was exposed to high-temperature immersion in water under hydraulic pressure. To understand the long-term service performance of the rod, immersions in water at 20 °C, 40 °C, or 60 °C under 20 MPa of pressure for 1 year were conducted on the water uptake and distribution in the rod. The water uptake data were fitted by Fickian diffusion law, and the diffusion coefficient and the maximum water uptake were derived. Water distribution in the rod as a function of the immersion time, temperature, and hydraulic pressure was analyzed theoretically. This study revealed the accelerating effects of the elevated temperatures and the hydraulic pressure on the water diffusion in the hybrid rod. Full article

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15 pages, 6143 KiB

Open AccessArticle

Microflow Mechanism of Oil Displacement by Viscoelastic Hydrophobically Associating Water-Soluble Polymers in Enhanced Oil Recovery

by Huiying Zhong, Yuanyuan Li, Weidong Zhang, Hongjun Yin, Jun Lu and Daizong Guo

Polymers 2018, 10(6), 628; https://doi.org/10.3390/polym10060628 - 7 Jun 2018

Cited by 37 | Viewed by 5752

Abstract

Polymer flooding plays an important role in enhanced oil recovery (EOR), particularly in China, where partially hydrolyzed polyacrylamide (HPAM) and hydrophobically associating water-soluble polymers (HAWP) are used in onshore and offshore reservoirs, respectively. Many researchers have highlighted the elasticity of HPAM, which can [...] Read more.

Polymer flooding plays an important role in enhanced oil recovery (EOR), particularly in China, where partially hydrolyzed polyacrylamide (HPAM) and hydrophobically associating water-soluble polymers (HAWP) are used in onshore and offshore reservoirs, respectively. Many researchers have highlighted the elasticity of HPAM, which can be used to improve the sweep efficiency, i.e., the ratio of the area swept by an injected fluid to the oil area. On the other hand, fewer studies exist on the elasticity of HAWP. In this study, we investigate the flow of HAWP and Xanthan solutions with identical viscosities in core experiments in terms of elasticity; results reveal that the HAWP can produce shear thickening in the core. The constitutive equation for the HAWP can be obtained using the simulation results matched with the experimental data. On the basis of these experiments, we established a two-phase flow model of a polymer and oil, including the continuity, momentum, constitutive, and phase equations. The volume-of-fluid (VOF) method was used to track the interface between the two phases. A complex pore model was established based on the glass-etched model used in the experiment. We used the OpenFOAM platform to solve the mathematical model. The saturation, pressure, and stress tensor distributions were obtained. The results show that the displacement efficiency increased as the elasticity of the polymer increased; accordingly, the elasticity can enlarge the sweep area and decrease the residual oil saturation. As the elasticity increases, the stresses (the first normal stress, second normal stress, and shear stress) increase. Finally, the results obtained in this study can be used as a guideline in polymer design, screening, and optimization in the polymer flooding oilfields. Full article

(This article belongs to the Special Issue Polymer Dynamics)

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13 pages, 3476 KiB

Open AccessArticle

Molecular Design and Property Prediction of Sterically Confined Polyimides for Thermally Stable and Transparent Materials

by Ki-Ho Nam, Hoi Kil Choi, Hyeonuk Yeo, Nam-Ho You, Bon-Cheol Ku and Jaesang Yu

Polymers 2018, 10(6), 630; https://doi.org/10.3390/polym10060630 - 7 Jun 2018

Cited by 19 | Viewed by 5257

Abstract

To meet the demand for next-generation flexible optoelectronic devices, it is crucial to accurately establish the chemical structure-property relationships of new optical polymer films from a theoretical point of view, prior to production. In the current study, computer-aided simulations of newly designed poly(ester [...] Read more.

To meet the demand for next-generation flexible optoelectronic devices, it is crucial to accurately establish the chemical structure-property relationships of new optical polymer films from a theoretical point of view, prior to production. In the current study, computer-aided simulations of newly designed poly(ester imide)s (PEsIs) with various side groups (–H, –CH₃, and –CF₃) and substituted positions were employed to study substituent-derived steric effects on their optical and thermal properties. From calculations of the dihedral angle distribution of the model compounds, it was found that the torsion angle of the C–N imide bonds was effectively constrained by the judicious introduction of di-, tetra-, and hexa-substituted aromatic diamines with –CF₃ groups. A high degree of fluorination of the PEsI repeating units resulted in weaker intra- and intermolecular conjugations. Their behavior was consistent with the molecular orbital energies obtained using density functional theory (DFT). In addition, various potential energy components of the PEsIs were investigated, and their role in glass-transition behavior was studied. The van der Waals energy (E_vdW) played a crucial role in the segmental chain motion, which had an abrupt change near glass-transition temperature (T_g). The more effective steric effect caused by –CF₃ substituents at the 3-position of the 4-aminophenyl group significantly improved the chain rigidity, and showed high thermal stability (T_g > 731 K) when compared with the –CH₃ substituent at the same position, by highly distorting (89.7°) the conformation of the main chain. Full article

(This article belongs to the Special Issue Thermal Properties and Applications of Polymers)

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12 pages, 1857 KiB

Open AccessArticle

Green Modification of Corn Stalk Lignin and Preparation of Environmentally Friendly Lignin-Based Wood Adhesive

by Sen Wang, Yalan Yu and Mingwei Di

Polymers 2018, 10(6), 631; https://doi.org/10.3390/polym10060631 - 7 Jun 2018

Cited by 52 | Viewed by 5911

Abstract

In this study, corn stalk lignin was used to react with non-volatile and non-toxic glyoxal under the catalysis of a sodium hydroxide solution, and a wood adhesive based on glyoxalated corn stalk lignin was prepared. The effect of the hydroxylation reaction on the [...] Read more.

In this study, corn stalk lignin was used to react with non-volatile and non-toxic glyoxal under the catalysis of a sodium hydroxide solution, and a wood adhesive based on glyoxalated corn stalk lignin was prepared. The effect of the hydroxylation reaction on the structure and properties of lignin were studied using Fourier transform infrared spectroscopy (FTIR), ultraviolet spectrophotometry (UV), thermogravimetric analysis (TGA), titration tests, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Compared with unmodified lignin, the glyoxalated corn stalk lignin had a significant improvement in hydroxyl content, activation, and thermal stability. At the same time, results from the GPC showed that the molecular weight increased compared with original corn stalk, possibly due to the secondary polycondensation reaction between lignin and glyoxal. Lignin-based environmental wood adhesives were prepared by mixing modified lignin and epichlorohydrin (ECH), and the dry strength of plywood reached 1.58 MPa. The mechanical strength and water resistance of plywood was improved significantly by mixing some aqueous emulsion into lignin-based adhesives, e.g., polyacrylic ester (AE) emulsion and aqueous polyurethane (PU) emulsion. Full article

(This article belongs to the Special Issue Polymer Hybrid Materials)

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20 pages, 5185 KiB

Open AccessArticle

Chemical and Electrochemical Synthesis of Polypyrrole Using Carrageenan as a Dopant: Polypyrrole/Multi-Walled Carbon Nanotube Nanocomposites

by Mostafizur Rahaman, Ali Aldalbahi, Mohammed Almoiqli and Shaykha Alzahly

Polymers 2018, 10(6), 632; https://doi.org/10.3390/polym10060632 - 7 Jun 2018

Cited by 57 | Viewed by 6412

Abstract

In this article, iota-carrageenan (IC) and kappa-carrageenan (KC) are used as dopants for the chemical and electrochemical synthesis of polypyrrole (PPy). The composites of chemically synthesized PPy with multi-walled carbon nanotubes (MWNTs) were prepared using an in situ technique. Both the dialyzed and [...] Read more.

In this article, iota-carrageenan (IC) and kappa-carrageenan (KC) are used as dopants for the chemical and electrochemical synthesis of polypyrrole (PPy). The composites of chemically synthesized PPy with multi-walled carbon nanotubes (MWNTs) were prepared using an in situ technique. Both the dialyzed and non-dialyzed IC and KC were used as dopants for electrochemical polymerization of pyrrole. Chemically synthesized PPy and PPy/MWNTs composites were studied by ultraviolet visible (UV-vis) absorption spectra to investigate the effect of the concentration and the incorporation of MWNTs. In addition, the electrical, thermal, mechanical, and microscopic characterizations of these films were performed to examine the effect of the dopants and MWNTs on these properties, along with their surface morphology. The films of electrochemically polymerized PPy were characterized using UV-vis absorption spectra, scanning electron microscopy, and cyclic voltammetry (CV). The results were then compared with the chemical polymerized PPy. Full article

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10 pages, 3335 KiB

Open AccessArticle

Enhancement of Rhodamine B Degradation by Ag Nanoclusters-Loaded g-C₃N₄ Nanosheets

by Thi Mai Oanh Le, Thi Hang Lam, Thi Nhung Pham, Tuan Cuong Ngo, Ngoc Diep Lai, Danh Bich Do and Van Minh Nguyen

Polymers 2018, 10(6), 633; https://doi.org/10.3390/polym10060633 - 8 Jun 2018

Cited by 27 | Viewed by 6455

Abstract

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) [...] Read more.

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) rather than well-crystallized nanoparticles are evidenced by X-ray diffraction patterns, SEM images, and XPS spectra. The deposition of Ag nanoclusters on the surface of g-C₃N₄ nanosheets affect the crystal structure and slightly reduce the band gap energy of g-C₃N₄. The sharp decrease of photoluminescence intensity indicates that g-C₃N₄/Ag heterojunctions successfully prevent the recombination of photo-generated electrons and holes. The photocatalytic activities of as-synthesized photocatalysts are demonstrated through the degradation of rhodamine B (RhB) solutions under Xenon lamp irradiation. It is demonstrated that the photocatalytic activity depends strongly on the molar concentration of Ag⁺ in the starting solution. The g-C₃N₄/Ag heterojunctions prepared from 0.01 M of Ag⁺ starting solution exhibit the highest photocatalytic efficiency and allow 100% degradation of RhB after being exposed for 60 min under a Xenon lamp irradiation, which is four times faster than that of pure g-C₃N₄ nanosheets. Full article

(This article belongs to the Special Issue Polymeric Photocatalysts and Gas Sensors)

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18 pages, 2968 KiB

Open AccessArticle

A Cellulose/Laponite Interpenetrated Polymer Network (IPN) Hydrogel: Controllable Double-Network Structure with High Modulus

by Fan Xie, Cécile Boyer, Victor Gaborit, Thierry Rouillon, Jérôme Guicheux, Jean-François Tassin, Valérie Geoffroy, Gildas Réthoré and Pierre Weiss

Polymers 2018, 10(6), 634; https://doi.org/10.3390/polym10060634 - 8 Jun 2018

Cited by 16 | Viewed by 6774

Abstract

Laponite XLS™, which is a synthetic clay of nanometric dimensions containing a peptizing agent, has been associated with silanized hydroxypropylmethylcellulose (Si-HPMC) to form, after crosslinking, a novel composite hydrogel. Different protocols of sample preparation were used, leading to different morphologies. A key result [...] Read more.

Laponite XLS™, which is a synthetic clay of nanometric dimensions containing a peptizing agent, has been associated with silanized hydroxypropylmethylcellulose (Si-HPMC) to form, after crosslinking, a novel composite hydrogel. Different protocols of sample preparation were used, leading to different morphologies. A key result was that the storage modulus of Si-HPMC/XLS composite hydrogel could be increased ten times when compared to that of pure Si-HPMC hydrogel using 2 wt % of Laponite. The viscoelastic properties of the composite formulations indicated that chemical and physical network structures co-existed in the Si-HPMC/XLS composite hydrogel. Images that were obtained from confocal laser scanning microscopy using labelled Laponite XLS in the composite hydrogels show two co-continuous areas: red light area and dark area. The tracking of fluorescent microspheres motions in the composite formulations revealed that the red-light area was a dense structure, whereas the dark area was rather loose without aggregated Laponite. This novel special double-network structure facilitates the composite hydrogel to be an adapted biomaterial for specific tissue engineering. Unfortunately, cytotoxicity’s assays suggested that XLS Laponites are cytotoxic at low concentration. This study validates that the hybrid interpenetrated network IPN hydrogel has a high modulus that has adapted for tissue engineering, but the cell’s internalization of Laponites has to be controlled. Full article

(This article belongs to the Special Issue Hydrophilic Polymers)

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10 pages, 1727 KiB

Open AccessArticle

Effects of Major Components of Synovial Fluid on the Morphology and Wear Rate of Polyetheretherketone (PEEK) Particles under an Accelerated Wear Process

by Chen-Ying Su, Shih-Shuan Huang and Hsu-Wei Fang

Polymers 2018, 10(6), 635; https://doi.org/10.3390/polym10060635 - 8 Jun 2018

Cited by 8 | Viewed by 3293

Abstract

Wear particle-induced biological responses are the major factors for the failure of total joint arthroplasties, but it is possible to improve the lubrication and reduce the wear of an artificial joint system. Polyetheretherketone (PEEK), with ultra-high molecular weight polyethylene, is a suitable bearing [...] Read more.

Wear particle-induced biological responses are the major factors for the failure of total joint arthroplasties, but it is possible to improve the lubrication and reduce the wear of an artificial joint system. Polyetheretherketone (PEEK), with ultra-high molecular weight polyethylene, is a suitable bearing material due to its resistance to fatigue strain. However, the effects of major compositions of synovial fluid on the wear of PEEK are unclear. We characterized the effects of three major components of synovial fluid including albumin, globulin, and phospholipids on the morphology and wear rate of PEEK wear particles. Our results demonstrated that the concentrations of albumin and globulin could affect the morphology of PEEK wear particles. In addition, a higher concentration of globulin and phospholipids (12.5 mg/mL) resulted in an increase in the amount of wear particles by 2.8- and 1.7-fold, respectively. In contrast, increasing albumin caused a reduction of wear particle numbers. These results indicate increasing concentration of albumin or reducing concentration of globulin or phospholipids has a better effect on reducing the numbers of wear particles and provides a potential solution of reducing PEEK wear particles, thus it can be more effectively applied in other biomedical systems. Full article

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19 pages, 2150 KiB

Open AccessArticle

Inhalable Fucoidan Microparticles Combining Two Antitubercular Drugs with Potential Application in Pulmonary Tuberculosis Therapy

by Ludmylla Cunha, Susana Rodrigues, Ana M. Rosa da Costa, M Leonor Faleiro, Francesca Buttini and Ana Grenha

Polymers 2018, 10(6), 636; https://doi.org/10.3390/polym10060636 - 8 Jun 2018

Cited by 37 | Viewed by 5911

Abstract

The pulmonary delivery of antitubercular drugs is a promising approach to treat lung tuberculosis. This strategy not only allows targeting the infected organ instantly, it can also reduce the systemic adverse effects of the antibiotics. In light of that, this work aimed at [...] Read more.

The pulmonary delivery of antitubercular drugs is a promising approach to treat lung tuberculosis. This strategy not only allows targeting the infected organ instantly, it can also reduce the systemic adverse effects of the antibiotics. In light of that, this work aimed at producing fucoidan-based inhalable microparticles that are able to associate a combination of two first-line antitubercular drugs in a single formulation. Fucoidan is a polysaccharide composed of chemical units that have been reported to be specifically recognised by alveolar macrophages (the hosts of Mycobacterium). Inhalable fucoidan microparticles were successfully produced, effectively associating isoniazid (97%) and rifabutin (95%) simultaneously. Furthermore, the produced microparticles presented adequate aerodynamic properties for pulmonary delivery with potential to reach the respiratory zone, with a mass median aerodynamic diameter (MMAD) between 3.6–3.9 µm. The formulation evidenced no cytotoxic effects on lung epithelial cells (A549), although mild toxicity was observed on macrophage-differentiated THP-1 cells at the highest tested concentration (1 mg/mL). Fucoidan microparticles also exhibited a propensity to be captured by macrophages in a dose-dependent manner, as well as an ability to activate the target cells. Furthermore, drug-loaded microparticles effectively inhibited mycobacterial growth in vitro. Thus, the produced fucoidan microparticles are considered to hold potential as pulmonary delivery systems for the treatment of tuberculosis. Full article

(This article belongs to the Special Issue Polymers from Renewable Resources)

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12 pages, 4082 KiB

Open AccessArticle

Facile Preparation of Highly Stretchable and Recovery Peptide-Polyurethane/Ureas

by Lin Gu, Yuanzhang Jiang and Jinlian Hu

Polymers 2018, 10(6), 637; https://doi.org/10.3390/polym10060637 - 8 Jun 2018

Cited by 8 | Viewed by 4623

Abstract

In this work, a new class of highly stretchable peptide-polyurethane/ureas (PUUs) were synthesized containing short β-sheet forming peptide blocks of poly(γ-benzyl-l-glutamate)-b-poly(propylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PPG-b-PBLG), isophorone diisocyanate as [...] Read more.

In this work, a new class of highly stretchable peptide-polyurethane/ureas (PUUs) were synthesized containing short β-sheet forming peptide blocks of poly(γ-benzyl-l-glutamate)-b-poly(propylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PPG-b-PBLG), isophorone diisocyanate as the hard segment, and polytetramethylene ether glycol as the soft phase. PBLG-b-PPG-b-PBLG with short peptide segment length (<10 residues) was synthesized by amine-initiated ring opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydrides (BLG-NCA), which shows mixed α-helix and β-sheet conformation, where the percent of β-sheet structure was above 48%. Morphological studies indicate that the obtained PUUs show β-sheet crystal and nanofibrous structure. Mechanical tests reveal the PUUs display medium tensile strength (0.25–4.6 MPa), high stretchability (>1600%), human-tissue-compatible Young’s modulus (226–513 KPa). Furthermore, the shape recovery ratio could reach above 85% during successive cycles at high strain (500%). In this study, we report a facile synthetic method to obtain highly stretchable and recovery peptide-polyurethane/urea materials, which will have various potential applications such as wearable and implantable electronics, and biomedical devices. Full article

(This article belongs to the Special Issue Protein Biopolymer)

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10 pages, 1633 KiB

Open AccessCommunication

Ring-Expansion/Contraction Radical Crossover Reactions of Cyclic Alkoxyamines: A Mechanism for Ring Expansion-Controlled Radical Polymerization

by Atsushi Narumi, Tetsuya Kobayashi, Masatsugu Yamada, Wolfgang H. Binder, Keigo Matsuda, Montaser Shaykoon Ahmed Shaykoon, Kazushi Enomoto, Moriya Kikuchi and Seigou Kawaguchi

Polymers 2018, 10(6), 638; https://doi.org/10.3390/polym10060638 - 8 Jun 2018

Cited by 7 | Viewed by 6009

Abstract

Macrocyclic polymers present an important class of macromolecules, displaying the reduced radius of gyration or impossibility to entangle. A rare approach for their synthesis is the ring expansion-controlled radical “vinyl” polymerization, starting from a cyclic alkoxyamine. We here describe ring-expansion radical crossover reactions [...] Read more.

Macrocyclic polymers present an important class of macromolecules, displaying the reduced radius of gyration or impossibility to entangle. A rare approach for their synthesis is the ring expansion-controlled radical “vinyl” polymerization, starting from a cyclic alkoxyamine. We here describe ring-expansion radical crossover reactions of cyclic alkoxyamines which run in parallel to chain-propagation reactions in the polymerization system. The radical crossover reactions extensively occurred at 105–125 °C, eventually producing high molecular weight polymers with multiple inherent dynamic covalent bonds (NOC bonds). A subsequent ring-contraction radical crossover reaction and the second ring-expansion radical crossover reaction are also described. The major products for the respective three stages were shown to possess cyclic morphologies by the molecular weight profiles and the residual ratios for the NOC bonds (φ in %). In particular, the high φ values ranging from ca. 80% to 98% were achieved for this cyclic alkoxyamine system. This result verifies the high availability of this system as a tool demonstrating the ring-expansion “vinyl” polymerization that allows them to produce macrocyclic polymers via a one-step vinyl polymerization. Full article

(This article belongs to the Special Issue Cyclic Polymers)

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23 pages, 6410 KiB

Open AccessFeature PaperArticle

Exploring the Long-Term Hydrolytic Behavior of Zwitterionic Polymethacrylates and Polymethacrylamides

by Eric Schönemann, André Laschewsky and Axel Rosenhahn

Polymers 2018, 10(6), 639; https://doi.org/10.3390/polym10060639 - 8 Jun 2018

Cited by 43 | Viewed by 6826

Abstract

The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are [...] Read more.

The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl-N,N-dimethyl) ammoniopropanesulfonate) (“sulfobetaine methacrylate”), and poly(3-(N-3-methacryamidopropyl-N,N-dimethyl)ammoniopropanesulfonate) (“sulfobetaine methacrylamide”) as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by ¹H NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile. Full article

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11 pages, 2300 KiB

Open AccessArticle

Post Self-Crosslinking of Phthalonitrile-Terminated Polyarylene Ether Nitrile Crystals

by Lifen Tong, Renbo Wei, Yong You and Xiaobo Liu

Polymers 2018, 10(6), 640; https://doi.org/10.3390/polym10060640 - 8 Jun 2018

Cited by 15 | Viewed by 3877

Abstract

A novel phthalonitrile-terminated polyaryl ether nitrile (PEN-Ph) was synthesized and characterized. The crystallization behavior coexisting with the crosslinking behavior in the PEN-Ph system was confirmed by rheological measurements. DSC was applied to study the crystallization kinetics and crosslinking reaction kinetics. Through the Avrami [...] Read more.

A novel phthalonitrile-terminated polyaryl ether nitrile (PEN-Ph) was synthesized and characterized. The crystallization behavior coexisting with the crosslinking behavior in the PEN-Ph system was confirmed by rheological measurements. DSC was applied to study the crystallization kinetics and crosslinking reaction kinetics. Through the Avrami equation modified by Jeziorny, the nonisothermal crystallization kinetics were analyzed, and the Avrami exponent of about 2.2 was obtained. The analysis results of more intuitive polaring optical microscopy (POM) and SEM indicated that the shape of the crystals is similar to spherical. Moreover, the activation energy of the crystallization behavior and crosslinking behavior were obtained by the Kissinger method, and the values were about 152.7 kJ·mol⁻¹ and 174.8 kJ·mol⁻¹, respectively. This suggests that the activation energy of the crystallization behavior is lower than that of the crosslinking behavior, indicating that the crystallization behavior is more likely to occur than the crosslinking behavior and the crystals of PEN-Ph can be self-crosslinked to form single-polymer composites. Full article

(This article belongs to the Special Issue Aromatic Polymers)

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16 pages, 3088 KiB

Open AccessArticle

Use of Irradiated Polymers after Their Lifetime Period

by David Manas, Miroslav Manas, Ales Mizera, Jan Navratil, Martin Ovsik, Katarina Tomanova and Stanislav Sehnalek

Polymers 2018, 10(6), 641; https://doi.org/10.3390/polym10060641 - 9 Jun 2018

Cited by 8 | Viewed by 3818

Abstract

This article deals with the study of the utilisation of irradiated HDPE products after their end-of-life cycle. Today, polymer waste processing is a matter of evermore intensive discussion. Common thermoplastic waste recycling—especially in the case of wastes with a defined composition—is generally well-known—and [...] Read more.

This article deals with the study of the utilisation of irradiated HDPE products after their end-of-life cycle. Today, polymer waste processing is a matter of evermore intensive discussion. Common thermoplastic waste recycling—especially in the case of wastes with a defined composition—is generally well-known—and frequently used. On the contrary, processing cross-linked plastics is impossible to do in the same way as with virgin thermoplastics—mainly due to the impossibility of remelting them. The possibility of using waste in the form of grit or a powder, made from cross-linked High Density PolyEthylene (rHDPEx) products, after their end-of-life cycle, as a filler for virgin Low Density PolyEthylene (LDPE) was tested in a matrix. It was found that both the mechanical behaviour and processability of new composites with an LDPE matrix, with rHDPEx as a filler, depend—to a high degree—on the amount of the filler. The composite can be processed up to 60% of the filler content. The Polymer Mixture Fluidity dropped significantly, in line with the amount of filler, while the mechanical properties, on the other hand, predominantly grew with the increasing amount of rHDPEx. Full article

(This article belongs to the Special Issue Model-Based Polymer Processing)

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16 pages, 10706 KiB

Open AccessArticle

Green Binder Based on Enzymatically Polymerized Eucalypt Kraft Lignin for Fiberboard Manufacturing: A Preliminary Study

by Susana Gouveia, Luis Alberto Otero, Carmen Fernández-Costas, Daniel Filgueira, Ángeles Sanromán and Diego Moldes

Polymers 2018, 10(6), 642; https://doi.org/10.3390/polym10060642 - 9 Jun 2018

Cited by 37 | Viewed by 5840

Abstract

The capability of laccase from Myceliophthora thermophila to drive oxidative polymerization of Eucalyptus globulus Kraft lignin (KL) was studied as a previous step before applying this biotechnological approach for the manufacturing of medium-density fiberboards (MDF) at a pilot scale. This method, which improves [...] Read more.

The capability of laccase from Myceliophthora thermophila to drive oxidative polymerization of Eucalyptus globulus Kraft lignin (KL) was studied as a previous step before applying this biotechnological approach for the manufacturing of medium-density fiberboards (MDF) at a pilot scale. This method, which improves the self-bonding capacity of wood fibers by lignin enzymatic cross-linking, mimics the natural process of lignification in living plants and trees. An interesting pathway to promote these interactions could be the addition of lignin to the system. The characterization of E. globulus KL after enzymatic treatment showed a decrease of phenolic groups as well as the aromatic protons without loss of aromaticity. There was also an extensive oxidative polymerization of the biomolecule. In the manufacture of self-bonded MDF, the synergy generated by the added lignin and laccase provided promising results. Thus, whenever laccase was present in the treatment, MDF showed an increase in mechanical and dimensional stability for increasing amounts of lignin. In a pilot scale, this method produced MDF that meets the requirements of the European standards for both thickness swell (TS) and internal bonding (IB) for indoor applications. Full article

(This article belongs to the Special Issue Polymers from Renewable Resources)

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21 pages, 14705 KiB

Open AccessArticle

Comparative Adhesion, Ageing Resistance, and Surface Properties of Wood Plastic Composite Treated with Low Pressure Plasma and Atmospheric Pressure Plasma Jet

by Andrés Jesús Yáñez-Pacios and José Miguel Martín-Martínez

Polymers 2018, 10(6), 643; https://doi.org/10.3390/polym10060643 - 9 Jun 2018

Cited by 32 | Viewed by 5855

Abstract

Wood plastic composites (WPCs) have poor adhesion properties due to their high surface concentration in non-polar polymers. In this work, two different plasma surface treatments, low pressure plasma (LPP) and atmospheric pressure plasma jet (APPJ), are proposed to increase the surface energy and [...] Read more.

Wood plastic composites (WPCs) have poor adhesion properties due to their high surface concentration in non-polar polymers. In this work, two different plasma surface treatments, low pressure plasma (LPP) and atmospheric pressure plasma jet (APPJ), are proposed to increase the surface energy and adhesion property of WPC made with polyethylene (PE-WPC). After optimizing the conditions for each plasma surface treatment, the surface modifications and adhesion of PE-WPC treated with LPP and APPJ were compared. The optimal surface modifications of PE-WPC were obtained by treatment with Argon (Ar): Oxygen (O₂) LPP for 90 s, and with air APPJ by using a plasma nozzle-WPC surface distance of one centimeter and speed of platform of one meter per minute. Both plasma treatments produced similar chemical modifications and surface energies on the PE-WPC surface. The ablation was more important for Ar:O₂ LPP treatment, and the air APPJ treatment produced more extensive chemical modifications and more homogeneously removal of the wood component of the surface, rendering the polymer surface smoother. Adhesion of PE-WPC was similarly improved by treatment with both plasmas, from 56 N/m in the as-received to 92–102 N/m in the plasma treated PE-WPC joints. The influence of ageing at 24 °C and 40% relative humidity of the adhesive joints made with PE-WPC surface and treated with Ar:O₂ LPP and APPJ plasmas was studied. In the joints made with plasma-treated PE-WPC aged under open air for more than one day, the adhesion decreased. An adhesive strength near to that of the joint made with the as-received PE-WPC was obtained after six days. However, if the adhesive joint was created immediately after plasma treatment and peeled at different times, the adhesion was maintained and even increased, and the hydrophobic recovery of the plasma-treated PE-WPC surface was inhibited. Full article

(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)

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18 pages, 2460 KiB

Open AccessArticle

Prediction of the Tensile Response of Carbon Black Filled Rubber Blends by Artificial Neural Network

by Ivan Kopal, Ivan Labaj, Marta Harničárová, Jan Valíček and Dušan Hrubý

Polymers 2018, 10(6), 644; https://doi.org/10.3390/polym10060644 - 9 Jun 2018

Cited by 28 | Viewed by 6225

Abstract

The precise experimental estimation of mechanical properties of rubber blends can be a very costly and time-consuming process. The present work explores the possibilities of increasing its efficiency by using artificial neural networks to study the mechanical behavior of these widely used materials. [...] Read more.

The precise experimental estimation of mechanical properties of rubber blends can be a very costly and time-consuming process. The present work explores the possibilities of increasing its efficiency by using artificial neural networks to study the mechanical behavior of these widely used materials. A multilayer feed-forward back-propagation artificial neural network model, with a strain and the carbon black content as input parameters and stress as an output parameter, has been developed to predict the uniaxial tensile response of vulcanized natural rubber blends with different contents of carbon black in the form of engineering stress-strain curves. A novel procedure has been created for the simulation of the optimized artificial neural network model with input datasets generated by a regression model of an experimental dependence of tensile strain-at-break on the carbon black content in the investigated blends. Errors of the prediction of experimental stress-strain curves, as well as of tensile strain-at-break, tensile stress-at-break and M100 tensile modulus were estimated for all simulated stress-strain curves. The present study demonstrated that the performance of a developed neural network model to predict the stress-strain curves of rubber blends with different contents of carbon black is also exceptionally high in the case of a network that had never learned the input data, which makes it a suitable tool for extensive use in practice. Full article

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16 pages, 2918 KiB

Open AccessFeature PaperArticle

Dual Stimuli-Responsive P(NIPAAm-co-SPA) Copolymers: Synthesis and Response in Solution and in Films

by Oliver Grimm and Felix H. Schacher

Polymers 2018, 10(6), 645; https://doi.org/10.3390/polym10060645 - 9 Jun 2018

Cited by 20 | Viewed by 6666

Abstract

We present the synthesis and solution properties of dual stimuli-responsive poly(N-isopropylacrylamide-co-spiropyran acrylate) (P(NIPAAm-co-SPA)) copolymers of varying composition prepared via nitroxide-mediated copolymerization. The resulting copolymers feature molar masses from 40,000 to 100,000 g/mol according to static light scattering [...] Read more.

We present the synthesis and solution properties of dual stimuli-responsive poly(N-isopropylacrylamide-co-spiropyran acrylate) (P(NIPAAm-co-SPA)) copolymers of varying composition prepared via nitroxide-mediated copolymerization. The resulting copolymers feature molar masses from 40,000 to 100,000 g/mol according to static light scattering and an SPA content of up to 5.3%. The latter was determined by ¹H NMR spectroscopy and UV–Vis spectroscopy. These materials exhibit reversible response upon irradiation in polymeric films for a minimum of three cycles; their response in solution to both light and temperature was also investigated in an aqueous TRIS buffer (pH 8). Irradiation was carried out using LED setups with wavelengths of 365 and 590 nm. In aqueous solution, a custom-made setup using a fiber-coupled 200 W Hg(Xe) lamp with 340 and 540 nm filters was used and additional heating of the copolymer solutions during irradiation allowed to study influence of the presence of either the spiropyran or merocyanine form on the cloud point temperature. Hereby, it was found that increasing the SPA content leads to a more pronounced difference between both states and decreasing cloud points in general. Full article

(This article belongs to the Special Issue Hydrophilic Polymers)

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14 pages, 4489 KiB

Open AccessArticle

Designing Green Plasticizers: Linear Alkyl Diol Dibenzoate Plasticizers and a Thermally Reversible Plasticizer

by Hanno C. Erythropel, Aurélie Börmann, Jim A. Nicell, Richard L. Leask and Milan Maric

Polymers 2018, 10(6), 646; https://doi.org/10.3390/polym10060646 - 9 Jun 2018

Cited by 19 | Viewed by 8933

Abstract

Several linear alkyl diol dibenzoate compounds, ranging from C3 to C6 in central diol length, were evaluated for their plasticizing effectiveness in blends with poly(vinyl chloride) (PVC). The results were compared to blends of PVC/di(2-ethylhexyl) phthalate (DEHP), the most commonly used commercial plasticizer. [...] Read more.

Several linear alkyl diol dibenzoate compounds, ranging from C3 to C6 in central diol length, were evaluated for their plasticizing effectiveness in blends with poly(vinyl chloride) (PVC). The results were compared to blends of PVC/di(2-ethylhexyl) phthalate (DEHP), the most commonly used commercial plasticizer. DEHP has come under scrutiny, due to its suspected endocrine-disrupting behaviour, and the proposed diol dibenzoates have previously been shown to have the potential to be green, safe candidates for DEHP replacement. The thermal and mechanical properties of PVC/dibenzoate blends were determined, and include glass transition temperature (T_g), the elongation at break, maximum stress, apparent moduli, torsional modulus, and surface hardness. The C3, C5, and C6 dibenzoates performed as well as or better than DEHP, with the exception of torsional modulus, further supporting their use as green plasticizers. For blends with 1,4-butanediol dibenzoate, differential scanning calorimetry and torsional temperature sweeps suggested that the compound partly crystallizes within PVC blends over the course of two days, thereby losing the ability to effectively plasticize PVC. However, upon heating to temperatures above 60 °C, effective plasticization was again observed. 1,4-Butanediol dibenzoate is thereby a reversible heat-activated plasticizer or processing aid with excellent plasticizer properties at mildly elevated temperatures. Full article

(This article belongs to the Special Issue Green Plasticizers for Polymers)

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24 pages, 15328 KiB

Open AccessArticle

Microstructure of Copolymers of Norbornene Based on Assignments of ¹³C NMR Spectra: Evolution of a Methodology

by Laura Boggioni, Simona Losio and Incoronata Tritto

Polymers 2018, 10(6), 647; https://doi.org/10.3390/polym10060647 - 9 Jun 2018

Cited by 14 | Viewed by 7098

Abstract

An overview of the methodologies to elucidate the microstructure of copolymers of ethylene and cyclic olefins through ¹³C Nuclear magnetic resonance (NMR) analysis is given. ¹³C NMR spectra of these copolymers are quite complex because of the presence of stereogenic carbons [...] Read more.

An overview of the methodologies to elucidate the microstructure of copolymers of ethylene and cyclic olefins through ¹³C Nuclear magnetic resonance (NMR) analysis is given. ¹³C NMR spectra of these copolymers are quite complex because of the presence of stereogenic carbons in the monomer unit and of the fact that chemical shifts of these copolymers do not obey straightforward additive rules. We illustrate how it is possible to assign ¹³C NMR spectra of cyclic olefin-based copolymers by selecting the proper tools, which include synthesis of copolymers with different comonomer content and by catalysts with different symmetries, the use of one- or two-dimensional NMR techniques. The consideration of conformational characteristics of copolymer chain, as well as the exploitation of all the peak areas of the spectra by accounting for the stoichoimetric requirements of the copolymer chain and the best fitting of a set of linear equation was obtained. The examples presented include the assignments of the complex spectra of poly(ethylene-co-norbornene (E-co-N), poly(propylene-co-norbornene (P-co-N) copolymers, poly(ethylene-co-4-Me-cyclohexane)s, poly(ethylene-co-1-Me-cyclopentane)s, and poly(E-ter-N-ter-1,4-hexadiene) and the elucidation of their microstructures. Full article

(This article belongs to the Special Issue NMR in Polymer Science)

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10 pages, 3336 KiB

Open AccessArticle

Application of the Products from the Maillard Reaction of Polyglutamic Acid and Glucose to Prepare Colored and Bioactive Silk

by Wen Zhang and Ren-Cheng Tang

Polymers 2018, 10(6), 648; https://doi.org/10.3390/polym10060648 - 10 Jun 2018

Cited by 11 | Viewed by 5502

Abstract

In this work, the Maillard reaction of polyglutamic acid (PGA) and glucose (Glc) was studied, and its functional, polymeric, and colored products were used to dye silk fiber with the aim of imparting bioactivities to silk. The UV–Vis spectroscopic analysis, which was employed [...] Read more.

In this work, the Maillard reaction of polyglutamic acid (PGA) and glucose (Glc) was studied, and its functional, polymeric, and colored products were used to dye silk fiber with the aim of imparting bioactivities to silk. The UV–Vis spectroscopic analysis, which was employed to monitor the reaction, revealed the rapid formation of yellowish-brown products at pH 12 and 90 °C, and the great impact of glucose content on the quantity of the products. The FT-IR analysis validated the formation of melanoidin colorants. The silk fiber dyed with the PGA/Glc reaction products at pH 3 displayed a yellowish-brown color, and had very good wash and rub fastness, but poor light fastness. The incorporation of the UV-absorbing moiety into the PGA/Glc reaction products enhanced their light stability. The SEM analysis revealed that the dyed silk fiber was covered by polymeric substances. The dyed silk exhibited durable antibacterial activity against Staphylococcus aureus and Escherichia coli, and good antioxidant activity. This research expands the application field of the Maillard reaction and provides a novel and eco-friendly approach to prepare the colored and bioactive silk materials. Full article

(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)

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9 pages, 10003 KiB

Open AccessArticle

Fabrication of Highly Packed Plasmonic Nanolens Array Using Polymer Nanoimprinted Nanodots for an Enhanced Fluorescence Substrate

by Mohsin Ali Badshah, Jun Kim, Hoyoung Jang and Seok-min Kim

Polymers 2018, 10(6), 649; https://doi.org/10.3390/polym10060649 - 10 Jun 2018

Cited by 13 | Viewed by 6179

Abstract

A simple and cost-effective fabrication method for plasmonic nanolens arrays (PNA) with a narrow gap has been proposed for fabricating enhanced fluorescence substrates, in which the fluorophores interacting with the enhanced electromagnetic field generated by localized surface plasmons provide a higher fluorescence signal. [...] Read more.

A simple and cost-effective fabrication method for plasmonic nanolens arrays (PNA) with a narrow gap has been proposed for fabricating enhanced fluorescence substrates, in which the fluorophores interacting with the enhanced electromagnetic field generated by localized surface plasmons provide a higher fluorescence signal. The PNA was fabricated by the sequential depositions of the SiO₂ and Ag layers on a UV-nanoimprinted nanodot array with a pitch of 500 nm, a diameter of 250 nm, and a height of 100 nm. During the deposition processes, the shape of the nanodots changed to that of nanolenses, and the gap between the nanolenses was decreased via sidewall deposition. To examine the feasibility of the fabricated PNA for enhanced fluorescence application, a streptavidin-Cy5 (SA-Cy5) conjugate dissolved in a saline buffer solution was spotted on the PNA, and the fluorescence signals of the SA-Cy5 were measured and compared with those on a bare glass substrate. The enhancement factor was affected by the gap between the nanolenses, and the maximum enhancement factor of ~128 was obtained from the PNA with a SiO₂ layer thickness of 150 nm and an Ag layer thickness of 100 nm. Finally, an electromagnetic field analysis was used to examine the fluorescence signal enhancement, and was conducted using rigorous coupled wave analysis. Full article

(This article belongs to the Special Issue Polymer Based Bio-Sensors)

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13 pages, 2493 KiB

Open AccessArticle

Effects of Sulfuric Acid on the Curing Behavior and Bonding Performance of Tannin–Sucrose Adhesive

by Zhongyuan Zhao, Yanfeng Miao, Ziqian Yang, Hua Wang, Ruijuan Sang, Yanchun Fu, Caoxing Huang, Zhihui Wu, Min Zhang, Shijing Sun, Kenji Umemura and Qiang Yong

Polymers 2018, 10(6), 651; https://doi.org/10.3390/polym10060651 - 11 Jun 2018

Cited by 40 | Viewed by 6869

Abstract

The development of biomaterials-based adhesives is one of the main research directions for the wood-based material industry. In previous research, tannin and sucrose were used as adhesive to manufacture particleboard. However, the reaction conditions need to be optimized. In this study, sulfuric acid [...] Read more.

The development of biomaterials-based adhesives is one of the main research directions for the wood-based material industry. In previous research, tannin and sucrose were used as adhesive to manufacture particleboard. However, the reaction conditions need to be optimized. In this study, sulfuric acid was added to the tannin–sucrose adhesive as a catalyst to improve the curing process. Thermal analysis, insoluble mass proportion, FT-IR, and solid state ¹³C NMR were used to investigate the effects of sulfuric acid on the curing behavior of tannin and sucrose. Thermal analysis showed weight loss and endotherm temperature reduced from 205 and 215 to 136 and 138 °C, respectively, by adding sulfuric acid. In case of the adhesive with pH = 1.0, the insoluble mass proportion achieved 81% at 160 °C, which was higher than the reference at 220 °C. FT-IR analysis of the uncured adhesives showed that adding sulfuric acid leads to hydrolysis of sucrose; then, glucose and fructose converted to 5-hydroxymehthylfurfural (HMF) and levulinic acid. Dimethylene ether bridges were observed by FT-IR analysis of the cured adhesives. The results of solid state ¹³C NMR spectrum indicated that 5-HMF participated in the curing process and formed methylene bridges with the C8 position of the resorcinol A-rings of tannin, whereas dimethylene ether bridges were detected as a major chemical chain of the polymer. Lab particleboards were produced using 20 wt % resin content at 180 °C and 10 min press time; the tannin–sucrose adhesive modified with sulfuric acid to pH = 1.0 exhibited better performance than the unmodified tannin–sucrose adhesive; the properties of the boards fulfilled the requirement of Japanese Industrial Standard (JIS) A5908 type 15. Full article

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18 pages, 5773 KiB

Open AccessArticle

Revealing the Mechanical Properties of Emulsion Polymer Isocyanate Film in Humid Environments

by Jing Guo, Hongjiu Hu, Kefeng Zhang, Yaolong He and Xingming Guo

Polymers 2018, 10(6), 652; https://doi.org/10.3390/polym10060652 - 11 Jun 2018

Cited by 14 | Viewed by 5252

Abstract

Knowledge of the mechanical behaviors of polymer film in humid environments is of great significance for predicting the long-term performance of emulsion polymer isocyanate (EPI) as a high-performance wood adhesive. A tri-copolymer latex was cross-linked by the general polymeric methylene diisocyanate (p [...] Read more.

Knowledge of the mechanical behaviors of polymer film in humid environments is of great significance for predicting the long-term performance of emulsion polymer isocyanate (EPI) as a high-performance wood adhesive. A tri-copolymer latex was cross-linked by the general polymeric methylene diisocyanate (p-MDI) and aqueous emulsified isocyanate (EMDI) at different loadings for preparing EPI. Furthermore, a series of uniaxial tension tests under different relative humidity (RH) were carried out on cured EPI samples before and after post-curing treatment, and the corresponding chemical structure, as well as the microstructure of polymers, was investigated in detail. In addition, a constitutive equation was formulated to calculate the viscoelastic characteristics of the adhesive layer. The results indicate that the EPI films reveal various kinds of intrinsic deformation as RH increases, and the tensile rupture stress and stiffness would obviously decrease, even at cross-linker weight ratios of up to 20%. Furthermore, the moisture resistance could be markedly improved by increasing the isocyanate content and post-cure. Importantly, EMDI-cross-linked film not only exhibits much better mechanical properties than that containing p-MDI at 0–80% RH, but is also more sensitive to post-cure. Finally, the derived viscoelastic model could efficiently track moisture-dependent stress-strain curves of EPI films, and the obtained relaxation time further reveals the influence mechanism of isocyanate and post-cure on the mechanical response of the cured polymer under moist conditions. Full article

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14 pages, 3980 KiB

Open AccessArticle

Crystal Orientation of Poly(l-Lactic Acid) Induced by Magnetic Alignment of a Nucleating Agent

by Ryosuke Kusumi, Sachi Teranishi, Fumiko Kimura, Masahisa Wada, Tsunehisa Kimura, Yoshiki Horikawa and Takahiko Kawai

Polymers 2018, 10(6), 653; https://doi.org/10.3390/polym10060653 - 11 Jun 2018

Cited by 8 | Viewed by 6225

Abstract

The orientation of poly(l-lactic acid) (PLLA) crystals was controlled through crystal growth from a magnetically oriented nucleating agent, phenylphosphonic acid zinc (PPAZn). The one-dimensional magnetically oriented microcrystal array of PPAZn microcrystals revealed the relationship between the magnetization and crystallographic axes in [...] Read more.

The orientation of poly(l-lactic acid) (PLLA) crystals was controlled through crystal growth from a magnetically oriented nucleating agent, phenylphosphonic acid zinc (PPAZn). The one-dimensional magnetically oriented microcrystal array of PPAZn microcrystals revealed the relationship between the magnetization and crystallographic axes in the PPAZn crystal. The PPAZn microcrystals were homogeneously dispersed in PLLA via melt mixing, which decreased the molecular weight of the PLLA component due to degradation. The PPAZn microcrystals in the molten PLLA were uniaxially aligned under an 8-T static or rotating magnetic field. The wide-angle X-ray diffraction and small-angle X-ray scattering patterns of the PPAZn/PLLA composite films crystallized under each magnetic field showed that the PLLA lamellae grew from the surface of the PPAZn microcrystals, which were uniaxially oriented along the easy- or hard-magnetization axis, with the c-axis of PLLA parallel to the bc-plane of PPAZn. It was also suggested that the greater nucleating effect of PPAZn on PLLA was derived not from geometrical matching, but from factors such as favorable interactions and/or the plate-like shape of the microcrystal. Full article

(This article belongs to the Special Issue Magnetic Field in Polymer Research)

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14 pages, 2196 KiB

Open AccessArticle

Free-Radical Copolymerization of Dibenzofulvene with (Meth)acrylates Leading to π-Stacked Copolymers

by Jiyue Luo, Yue Wang and Tamaki Nakano

Polymers 2018, 10(6), 654; https://doi.org/10.3390/polym10060654 - 11 Jun 2018

Cited by 5 | Viewed by 5746

Abstract

Copolymerizations of dibenzofulvene (DBF) with methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), methyl acrylate (MA), and 2-hydroxyethyl acrylate (HEA) were conducted under free radical conditions in toluene using α,α′-azobisisobutylonitrile (AIBN) as the initiator. In the copolymerizations, DBF indicated much higher reactivity than the comonomers, [...] Read more.

Copolymerizations of dibenzofulvene (DBF) with methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), methyl acrylate (MA), and 2-hydroxyethyl acrylate (HEA) were conducted under free radical conditions in toluene using α,α′-azobisisobutylonitrile (AIBN) as the initiator. In the copolymerizations, DBF indicated much higher reactivity than the comonomers, and the products comprised mainly of DBF units. NMR, UV, and fluorescence spectra, as well as electrochemical features indicated that the copolymers possess both isolated and rather short, sequential (meth)acrylate units, as well as π-stacked and unstacked DBF sequences. Isolated (meth)acrylate units are proposed to be sandwiched between DBF units. The ratios of π-stacked and unstacked side-chain fluorene groups of DBF units in excited states were accurately determined on the basis of fluorescent emission spectra; DBF units are mostly π-stacked in excited states as disclosed by fluorescence spectra. Two types of π-stacked sequences were suggested to be present in the ground state by electrochemical analysis. The copolymers exhibited higher solubility than pure poly(DBF). Full article

(This article belongs to the Special Issue π-Stacked Polymers)

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18 pages, 3783 KiB

Open AccessArticle

Local Order and Dynamics of Nanoconstrained Ethylene-Butylene Chain Segments in SEBS

by Michele Mauri, George Floudas and Roberto Simonutti

Polymers 2018, 10(6), 655; https://doi.org/10.3390/polym10060655 - 11 Jun 2018

Cited by 11 | Viewed by 5083

Abstract

Subtle alterations in the mid-block of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene (SEBS) have a significant impact on the mechanical properties of the resulting microphase separated materials. In samples with high butylene content, the ethylene-co-butylene (EB) phase behaves as a rubber, [...] Read more.

Subtle alterations in the mid-block of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene (SEBS) have a significant impact on the mechanical properties of the resulting microphase separated materials. In samples with high butylene content, the ethylene-co-butylene (EB) phase behaves as a rubber, as seen by differential scanning calorimetry (DSC), time domain (TD) and Magic Angle Spinning (MAS) NMR, X-ray scattering at small (SAXS), and wide (WAXS) angles. In samples where the butylene content is lower—but still sufficient to prevent crystallization in bulk EB—the DSC thermogram presents a broad endothermic transition upon heating from 221 to 300 K. TD NMR, supported by WAXS and dielectric spectroscopy measurements, probed the dynamic phenomena of EB during this transition. The results suggest the existence of a rotator phase for the EB block below room temperature, as a result of nanoconfinement. Full article

(This article belongs to the Special Issue NMR in Polymer Science)

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12 pages, 9237 KiB

Open AccessArticle

Thermoresponsive Microgel Coatings as Versatile Functional Compounds for Novel Cell Manipulation Tools

by Katja Uhlig, Thomas Wegener, Yvonne Hertle, Johannes Bookhold, Magnus Jaeger, Thomas Hellweg, Andreas Fery and Claus Duschl

Polymers 2018, 10(6), 656; https://doi.org/10.3390/polym10060656 - 12 Jun 2018

Cited by 29 | Viewed by 5357

Abstract

For the effective use of live cells in biomedicine as in vitro test systems or in biotechnology, non-invasive cell processing and characterisation are key elements. Thermoresponsive polymer coatings have been demonstrated to be highly beneficial for controlling the interaction of adherent cells through [...] Read more.

For the effective use of live cells in biomedicine as in vitro test systems or in biotechnology, non-invasive cell processing and characterisation are key elements. Thermoresponsive polymer coatings have been demonstrated to be highly beneficial for controlling the interaction of adherent cells through their cultivation support. However, the widespread application of these coatings is hampered by limitations in their adaptability to different cell types and because the full range of applications has not yet been fully explored. In the work presented here, we address these issues by focusing on three different aspects. With regard to the first aspect, by using well-defined laminar flow in a microchannel, a highly controllable and reproducible shear force can be applied to adherent cells. Employing this tool, we demonstrate that cells can be non-invasively detached from a support using a defined shear flow. The second aspect relates to the recent development of simple methods for patterning thermoresponsive coatings. Here, we show how such patterned coatings can be used for improving the handling and reliability of a wound-healing assay. Two pattern geometries are tested using mouse fibroblasts and CHO cells. In terms of the third aspect, the adhesiveness of cells depends on the cell type. Standard thermoresponsive coatings are not functional for all types of cells. By coadsorbing charged nanoparticles and thermoresponsive microgels, it is demonstrated that the adhesion and detachment behaviour of cells on such coatings can be modulated. Full article

(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)

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11 pages, 3386 KiB

Open AccessArticle

Fluorescent Polyion Complex for the Detection of Sodium Dodecylbenzenesulfonate

by Shuai Liu, Cun Hu, Jianbin Huang and Yun Yan

Polymers 2018, 10(6), 657; https://doi.org/10.3390/polym10060657 - 12 Jun 2018

Cited by 9 | Viewed by 3517

Abstract

Polyion complexes have been known about for decades, with their applications mainly restricted to drug and gene delivery. In this study, we show that by the introduction of fluorescent charged molecules into a polyion complex, it can be used as a specific detection [...] Read more.

Polyion complexes have been known about for decades, with their applications mainly restricted to drug and gene delivery. In this study, we show that by the introduction of fluorescent charged molecules into a polyion complex, it can be used as a specific detection system for surfactants. The fluorescence of 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) is quenched in the ionic complex, while it can be recovered with the addition of the surfactant sodium dodecylbenzenesulfonate (SDBS), due to the stronger interaction between SDBS and the polyelectrolyte. This leads to a drastic color change of the solution, and a recovery of the strong emission of HPTS. Specifically, the fluorescence is linearly proportional to the concentration of SDBS, thus it can be used for the qualitative detection of SDBS. Furthermore, the detection limit for SDBS can be up to the order of 10⁻¹⁰ M. We believe that competitive dissociation of the ionic complex can be used as a general approach for the construction of new functional materials. Full article

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10 pages, 1934 KiB

Open AccessArticle

Study on the Aging Behavior of Natural Rubber/Butadiene Rubber (NR/BR) Blends Using a Parallel Spring Model

by Byungwoo Moon, Jongmin Lee, Soo Park and Chang-Sung Seok

Polymers 2018, 10(6), 658; https://doi.org/10.3390/polym10060658 - 12 Jun 2018

Cited by 55 | Viewed by 8027

Abstract

Natural rubber/butadiene rubber (NR/BR) blends are widely used in industrial areas for absorbing vibrations and shocks because of their excellent elastic stability. However, when an industrial-equipment surface is exposed to sunlight and oxygen over a long period of time, the rubber hardens. As [...] Read more.

Natural rubber/butadiene rubber (NR/BR) blends are widely used in industrial areas for absorbing vibrations and shocks because of their excellent elastic stability. However, when an industrial-equipment surface is exposed to sunlight and oxygen over a long period of time, the rubber hardens. As a result, the tensile properties of the rubber material and the behavior of the strain-energy density function are changed, greatly reducing the performance of the rubber product. However, only a few experimental studies on the aging characteristics of NR/BR blends are available, and it is difficult to find a study that analyzes the organic relationship of the changes in the mechanical (stress–strain curves, strain-energy density, etc.) and chemical (cross-linked structure, crosslink density, etc.) properties. In this study, a swelling test was performed on an aged rubber compound, and the result was substituted into the Flory–Rehner equation to obtain the quantitative crosslink density. The results revealed a linear relationship between the strain-energy density (SED) and the crosslink density (CLD) when the cross-linked structure increase was represented by a parallel spring model. Finally, the relationship between the strain-energy density and the crosslink density was summarized as a formula, and a method for predicting the aging behavior of NR/BR blends using the crosslink density was proposed. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer-Based Materials)

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15 pages, 3647 KiB

Open AccessArticle

Renewable Polysaccharides as Supports for Palladium Phosphine Catalysts

by Oshrat Levy-Ontman, Shira Biton, Boris Shlomov and Adi Wolfson

Polymers 2018, 10(6), 659; https://doi.org/10.3390/polym10060659 - 12 Jun 2018

Cited by 30 | Viewed by 4913

Abstract

The investigation of the use of polysaccharides derived from natural sources to support metal catalysis has been the focus of several studies. Even though these molecules seem to be attractive materials, their full potential for use in support of heterogeneous catalysis still needs [...] Read more.

The investigation of the use of polysaccharides derived from natural sources to support metal catalysis has been the focus of several studies. Even though these molecules seem to be attractive materials, their full potential for use in support of heterogeneous catalysis still needs to be revealed. To that end, we developed a new preparation technique for polysaccharide-based palladium catalysts by immobilizing the palladium phosphine complexes on various renewable polysaccharides. The Suzuki cross-coupling in ethanol, using PdCl₂(TPPTS)₂ supported by various polysaccharides, was determined by gas chromatography and compared to homogeneous free-catalyst support. The PdCl₂(TPPTS)₂, that was immobilized on red algae supports, was successfully used as a heterogeneous catalyst in the Suzuki cross-coupling reaction, yielding high activity, higher than that of the homogeneous complex, without leaching. The FTIR spectrometry of representative heterogeneous polysaccharide-based TPPTS–PdCl₂ catalysts was compared to that of native polysaccharide and polysaccharide-based TPP–PdCl₂ catalysts, indicated on new bands, suggesting that the heterogenization occurs via interactions between the sulfonate group on the TPPTS and the hydroxyl groups on the polysaccharides. EDS and XPS analysis were also performed, confirming that the Pd complex was embedded within the i-carrageenan. A comparison of SEM images of i-carrageenan preparations also shed light on the interaction occurring between the polysaccharides and the TPPTS. Full article

(This article belongs to the Collection Polysaccharides)

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15 pages, 2908 KiB

Open AccessArticle

pH-Responsive Hybrid Hydrogels as Antibacterial and Drug Delivery Systems

by Shabnam Sattari, Abbas Dadkhah Tehrani and Mohsen Adeli

Polymers 2018, 10(6), 660; https://doi.org/10.3390/polym10060660 - 13 Jun 2018

Cited by 62 | Viewed by 7792

Abstract

This study describes the design and synthesis of organic–inorganic hybrid hydrogels based on an interpenetrating polymer network (IPN) composed of polyaspartic acid crosslinked by graphene nanosheets as the primary network and poly(acrylamide-co-acrylic acid) as the secondary network. Silver, copper oxide, and zinc oxide [...] Read more.

This study describes the design and synthesis of organic–inorganic hybrid hydrogels based on an interpenetrating polymer network (IPN) composed of polyaspartic acid crosslinked by graphene nanosheets as the primary network and poly(acrylamide-co-acrylic acid) as the secondary network. Silver, copper oxide, and zinc oxide nanoparticles were formed within the gel matrix, and the obtained hydrogel was applied to a load and controlled release of curcumin. The loading of curcumin and the release of this drug from the gels depended on the nanoparticle’s (NP’s) content of hydrogels as well as the pH of the medium. The synthesized hydrogels showed antibacterial activity against E. coli and S. aureus bacteria. The ability of the synthesized hydrogels to incapacitate bacteria and their loading capacity and controlled release of curcumin qualify them for future therapies such as wound-dressing applications. Full article

(This article belongs to the Special Issue Polymers for Therapy and Diagnostics)

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12 pages, 4713 KiB

Open AccessArticle

Tensile Creep Behavior of Quasi-Unidirectional E-Glass Fabric Reinforced Polypropylene Composite

by Zhanyu Zhai, Bingyan Jiang and Dietmar Drummer

Polymers 2018, 10(6), 661; https://doi.org/10.3390/polym10060661 - 13 Jun 2018

Cited by 18 | Viewed by 6157

Abstract

The present work addressed the creep behavior of quasi-unidirectional E-glass fabric reinforced polypropylene composites under off-axis tensile loading. A series of creep tests were performed on the composite at three different loading stress levels. The creep response of off-axis samples of quasi-unidirectional composites [...] Read more.

The present work addressed the creep behavior of quasi-unidirectional E-glass fabric reinforced polypropylene composites under off-axis tensile loading. A series of creep tests were performed on the composite at three different loading stress levels. The creep response of off-axis samples of quasi-unidirectional composites under a constant loading level can be clearly observed. A phenomenological viscoplasticity model was built for describing the creep behavior of the composite. To improve the accuracy of prediction, cyclic loading-unloading tests were adopted to determine the material constants in the model. The predicted results in terms of the strains after a load over a period of time were found to be satisfactory, compared with the experimental results. In addition, same failure mechanism was found in off-axis samples under quasi-static and creep loading cases. Full article

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13 pages, 3026 KiB

Open AccessArticle

Synthesis and Characterization of Poly(1,4,7-Trioxacycloundecane-8,11-dione) Macrocyclic Functionalized Hydrogel for High Selectivity Adsorption and Complexation of Bismuth Ion

by Brian A. Omondi, Hirotaka Okabe, Yoshiki Hidaka and Kazuhiro Hara

Polymers 2018, 10(6), 662; https://doi.org/10.3390/polym10060662 - 13 Jun 2018

Cited by 5 | Viewed by 3739

Abstract

Macrocyclic functional hydrogels incorporating new poly cyclic active sites (1,4,7-trioxacycloundecane-8,11-dione) within their entire network, have been synthesized. Using the high-dilution coupling of the bi-functional monomers maleic acid and bis(chloroethyl)ether in a sol-gel chemistry synthesis, 11-membered chelate rings infused with three oxygen donor atoms [...] Read more.

Macrocyclic functional hydrogels incorporating new poly cyclic active sites (1,4,7-trioxacycloundecane-8,11-dione) within their entire network, have been synthesized. Using the high-dilution coupling of the bi-functional monomers maleic acid and bis(chloroethyl)ether in a sol-gel chemistry synthesis, 11-membered chelate rings infused with three oxygen donor atoms were created and characterized, and their structures confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopic analyses. The macrocyclic gel, designed for selective host-guest adsorption and complexation of metal substrates, was initially tested against an aqueous set of 14 metal competitive solutions, where it demonstrated exclusive selectivity for Bi³⁺_aq, with the other metals exhibiting zero adsorption. Further analysis using binary and single ion Bi³⁺-containing solutions showed a near-complete removal of Bi³⁺ using this polycyclic hydrogel, with 98% extraction efficiency and q = 9.80 mg/g. These results clearly confirm that the 1,4,7-trioxacycloundecane-8,11-dione cyclic sites are most suitable for high selectivity and capture of Bi. The metal substrates were entrapped within the 1,4,7-trioxacycloundecane-8,11-dione cyclic sites. Evidently, by exploiting the host-guest complexation chemistry of macrocycles, we were able to design hydrogel adsorbents whose networks were comprised entirely of macrocyclic active groups for possible purification works of copper involving bismuth impurities, and/or for efficient selective uptake and recovery of bismuth trace ions existing in highly competitive environments such as sea water. Full article

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13 pages, 4089 KiB

Open AccessArticle

Preparation and Properties of 3D Printed Alginate–Chitosan Polyion Complex Hydrogels for Tissue Engineering

by Qiongqiong Liu, Qingtao Li, Sheng Xu, Qiujian Zheng and Xiaodong Cao

Polymers 2018, 10(6), 664; https://doi.org/10.3390/polym10060664 - 14 Jun 2018

Cited by 183 | Viewed by 14741

Abstract

Three-dimensional (3D) printing holds great potential for preparing sophisticated scaffolds for tissue engineering. As a result of the shear thinning properties of an alginate solution, it is often used as 3D printing ink. However, it is difficult to prepare scaffolds with complexity structure [...] Read more.

Three-dimensional (3D) printing holds great potential for preparing sophisticated scaffolds for tissue engineering. As a result of the shear thinning properties of an alginate solution, it is often used as 3D printing ink. However, it is difficult to prepare scaffolds with complexity structure and high fidelity, because the alginate solution has a low viscosity and alginate hydrogels prepared with Ca²⁺ crosslinking are mechanically weak. In this work, chitosan powders were dispersed and swelled in an alginate solution, which could effectively improve the viscosity of an alginate solution by 1.5–4 times. With the increase of chitosan content, the shape fidelity of the 3D printed alginate–chitosan polyion complex (AlCh PIC) hydrogels were improved. Scanning electron microscope (SEM) photographs showed that the lateral pore structure of 3D printed hydrogels was becoming more obvious. As a result of the increased reaction ion pairs in comparison to the alginate hydrogels that were prepared with Ca²⁺ crosslinking, AlCh PIC hydrogels were mechanically strong, and the compression stress of hydrogels at a 90% strain could achieve 1.4 MPa without breaking. In addition, human adipose derived stem cells (hASCs) adhered to the 3D printed AlCh PIC hydrogels and proliferated with time, which indicated that the obtained hydrogels were biocompatible and could potentially be used as scaffolds for tissue engineering. Full article

(This article belongs to the Collection Polysaccharides)

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25 pages, 7092 KiB

Open AccessArticle

Trithiocarbonate-Functionalized PNiPAAm-Based Nanocomposites for Antimicrobial Properties

by Milène Tan, Lenke Horvàth, Priscilla S. Brunetto and Katharina M. Fromm

Polymers 2018, 10(6), 665; https://doi.org/10.3390/polym10060665 - 14 Jun 2018

Cited by 3 | Viewed by 5480

Abstract

In this study, four trithiocarbonate-functionalized PNiPAAms with different molecular weights were synthesized and used as a matrix to form composites with silver nanoparticles. Nanocomposites with several polymer-to-silver ratios P:Ag⁺ were prepared in order to evaluate the influence of silver loading. UV studies [...] Read more.

In this study, four trithiocarbonate-functionalized PNiPAAms with different molecular weights were synthesized and used as a matrix to form composites with silver nanoparticles. Nanocomposites with several polymer-to-silver ratios P:Ag⁺ were prepared in order to evaluate the influence of silver loading. UV studies showed a thermoresponsive behavior of the nanocomposites with a thermo-reversibility according to cooling-heating cycles. Release kinetics demonstrated that the release of silver ions is mainly influenced by the size of the silver nanoparticles (AgNPs), which themselves depend on the polymer length. Antimicrobial tests against E. coli and S. aureus showed that some of the nanocomposites are antimicrobial and even full killing could be induced. Full article

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18 pages, 7269 KiB

Open AccessArticle

Fused Deposition Modeling of ABS-Barium Titanate Composites: A Simple Route towards Tailored Dielectric Devices

by Bilal Khatri, Karl Lappe, Mathis Habedank, Tobias Mueller, Christof Megnin and Thomas Hanemann

Polymers 2018, 10(6), 666; https://doi.org/10.3390/polym10060666 - 14 Jun 2018

Cited by 97 | Viewed by 9323

Abstract

A process for the development, characterization and correlation of composite materials for 3D printing is presented, alongside the processing of a polymer-ceramic functional composite using fused deposition modeling (FDM). The composite was developed using acrylonitrile butadiene styrene (ABS) as the matrix material filled [...] Read more.

A process for the development, characterization and correlation of composite materials for 3D printing is presented, alongside the processing of a polymer-ceramic functional composite using fused deposition modeling (FDM). The composite was developed using acrylonitrile butadiene styrene (ABS) as the matrix material filled with barium titanate (BT) micro-powder up to 35 vol % (74.2 wt %). The ABS-BT composites exhibited a shear thinning behavior with increasing ceramic content. The composite was 3D printed into structural and functional test samples using FDM by adapting and optimizing the print parameters. Structural characterization revealed increasingly brittle behavior at higher filler ratios, with the ultimate tensile strength falling from 25.5 MPa for pure ABS to 13.7 MPa for the ABS-35 vol % BT composite. Four-point flexural tests showed a similar decrease in flexural strength with increasing ceramic content. Functional characterization revealed an increase in the relative permittivity at 200 kHz from 3.08 for pure ABS to 11.5 for the composite with 35 vol % BT. These results were correlated with the Maxwell-Garnett and Jayasundere-Smith effective medium models. The process described in this work can be used for other 3D printing processes and provides a framework for the rapid prototyping of functional composites into functional parts with reliable properties. The ABS-BT composite shows promise as a functional dielectric material, with potential applications as capacitors and light-weight passive antennas. Full article

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17 pages, 8430 KiB

Open AccessArticle

Effect of Graphene Nano-Additives on the Local Mechanical Behavior of Derived Polymer Nanocomposites

by Mostapha Tarfaoui, Khalid Lafdi, Imane Beloufa, Debora Daloia and Ali Muhsan

Polymers 2018, 10(6), 667; https://doi.org/10.3390/polym10060667 - 15 Jun 2018

Cited by 20 | Viewed by 5198

Abstract

In this study, indentation tests of graphene-based polymer nanocomposites were carried out to determine the local elastic mechanical properties. The samples consist of epoxy matrix with graphene additives. Additives were added at levels of 0% as a control, 0.5%, 1%, 2.5%, 5% and [...] Read more.

In this study, indentation tests of graphene-based polymer nanocomposites were carried out to determine the local elastic mechanical properties. The samples consist of epoxy matrix with graphene additives. Additives were added at levels of 0% as a control, 0.5%, 1%, 2.5%, 5% and 10% by weight. The local elastic properties such as moduli and hardness were calculated. After each indentation, the prints were characterized using scanning electron microscopy (SEM). It seems that the local mechanical properties of nanocomposite samples were improved as the amount of nano-additives increased. Based on the curve displacement and surface imaging, we can conclude that the nano-additives influenced the overall plastic mechanical behavior of the samples. For simulating micro-indentation test, a finite element analysis model was developed using ABAQUS software and compared to experimental tests. Good correlation was observed. Full article

(This article belongs to the Special Issue Applications of Graphene and Fullerene Nanocomposites)

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18 pages, 6555 KiB

Open AccessArticle

Visco-Hyperelastic Model with Damage for Simulating Cyclic Thermoplastic Elastomers Behavior Applied to an Industrial Component

by Rafael Tobajas, Daniel Elduque, Elena Ibarz, Carlos Javierre, Alfonso F. Canteli and Luis Gracia

Polymers 2018, 10(6), 668; https://doi.org/10.3390/polym10060668 - 15 Jun 2018

Cited by 14 | Viewed by 5787

Abstract

In this work a nonlinear phenomenological visco-hyperelastic model including damage consideration is developed to simulate the behavior of Santoprene 101-73 material. This type of elastomeric material is widely used in the automotive and aeronautic sectors, as it has multiple advantages. However, there are [...] Read more.

In this work a nonlinear phenomenological visco-hyperelastic model including damage consideration is developed to simulate the behavior of Santoprene 101-73 material. This type of elastomeric material is widely used in the automotive and aeronautic sectors, as it has multiple advantages. However, there are still challenges in properly analyzing the mechanical phenomena that these materials exhibit. To simulate this kind of material a lot of theories have been exposed, but none of them have been endorsed unanimously. In this paper, a new model is presented based on the literature, and on experimental data. The test samples were extracted from an air intake duct component of an automotive engine. Inelastic phenomena such as hyperelasticity, viscoelasticity and damage are considered singularly in this model, thus modifying and improving some relevant models found in the literature. Optimization algorithms were used to find out the model parameter values that lead to the best fit of the experimental curves from the tests. An adequate fitting was obtained for the experimental results of a cyclic uniaxial loading of Santoprene 101-73. Full article

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14 pages, 3836 KiB

Open AccessArticle

Heterogeneous Catalytic Composites from Palladium Nanoparticles in Montmorillonite Intercalated with Poly (Vinyl Pyrrolidone) Chains

by Mengdie Xu, Jing Zhao, Guiqing Shu, Qi Liu and Minfeng Zeng

Polymers 2018, 10(6), 669; https://doi.org/10.3390/polym10060669 - 15 Jun 2018

Cited by 10 | Viewed by 4245

Abstract

In this study, poly (vinyl pyrrolidone) (PVP) chains intercalated montmorillonite (MMT) matrices has been demonstrated as an excellent scaffolding material for the immobilization of palladium (Pd) nanoparticles to prepare efficient heterogeneous catalysts for Heck reactions. Multiple layers (up to four) of PVP chains [...] Read more.

In this study, poly (vinyl pyrrolidone) (PVP) chains intercalated montmorillonite (MMT) matrices has been demonstrated as an excellent scaffolding material for the immobilization of palladium (Pd) nanoparticles to prepare efficient heterogeneous catalysts for Heck reactions. Multiple layers (up to four) of PVP chains can intercalate the interlayer space of the MMT, resulting in an increase therein from 1.25 to 3.22 nm. MMT/PVP with PVP loading (20%) was selected as the platform for the immobilization of Pd. The in-situ reduction of the chelated Pd²⁺ into Pd⁰ in the interlayer space of MMT/PVP composite could be easily achieved. For the prepared Pd@MMT/PVP catalytic composite, a unique maze-like microstructure of Pd nanoparticles tightly encaged by PVP chains and by lamellae of layered silica has been detected by high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). Furthermore, the microstructure is well elucidated in molecular level by positron annihilation lifetime analysis of the Pd@MMT/PVP catalytic composite. The prepared Pd@MMT/PVP catalysts were highly active for the Heck coupling reactions between aromatic halides and alkenes, and could be recycled 9 times without significant decreases in coupling yields. The excellent comprehensive catalytic performances of the Pd@MMT/PVP catalytic composites are mainly attributed to their unique maze-like microstructure. Full article

(This article belongs to the Special Issue Polymer-Clay (Nano)Composites)

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14 pages, 4662 KiB

Open AccessArticle

Modification of Alkali Lignin with Poly(Ethylene Glycol) Diglycidyl Ether to Be Used as a Thickener in Bio-Lubricant Formulations

by Esperanza Cortés-Triviño, Concepción Valencia, Miguel A. Delgado and José M. Franco

Polymers 2018, 10(6), 670; https://doi.org/10.3390/polym10060670 - 16 Jun 2018

Cited by 37 | Viewed by 7248

Abstract

Considerable efforts are currently being made by the academic community and industry, aiming to develop environmentally friendly lubricants with suitable technical features for their performance. In this context, lignin could be considered a promising candidate to be used as a bio-sourced thickening agent [...] Read more.

Considerable efforts are currently being made by the academic community and industry, aiming to develop environmentally friendly lubricants with suitable technical features for their performance. In this context, lignin could be considered a promising candidate to be used as a bio-sourced thickening agent to formulate eco-friendly lubricating greases. In this work, alkali lignin (AL) was chemically modified with poly(ethylene glycol) diglycidyl ether (PEGDE). Afterwards, the epoxidized lignin was properly dispersed in castor oil (CO) in order to obtain an oleogel for lubricant applications. The epoxidized lignins were characterized by means of epoxy index determination, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The epoxide-functionalized lignin-based oleogels were analyzed from both rheological and tribological points of view. It was found that the viscosity, consistency and viscoelastic functions of these oleogels clearly increased with the epoxy index of the epoxide-modified lignin compound. Thermo-rheological characterization of these oleogels revealed a slight thermal dependence of the viscoelastic moduli below 100 °C, but a significant softening above that critical temperature. In general, these oleogels showed low values of the friction coefficient under the mixed lubrication regime as compared to the neat castor oil. Full article

(This article belongs to the Special Issue Lignin Polymers: Structures, Reactions and Applications)

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11 pages, 3773 KiB

Open AccessArticle

A Numerical and Experimental Study on a Pre-Twisted Ring Spinning System

by Keyi Wang, Wenliang Xue and Longdi Cheng

Polymers 2018, 10(6), 671; https://doi.org/10.3390/polym10060671 - 16 Jun 2018

Cited by 5 | Viewed by 5355

Abstract

The ring spinning process is the most widely used method in the spinning industry. Nowadays, the labor cost become more and more expensive, and it is essential to improve productivity. For increasing the productivity, a modification of adding a pre-twister and holding roller [...] Read more.

The ring spinning process is the most widely used method in the spinning industry. Nowadays, the labor cost become more and more expensive, and it is essential to improve productivity. For increasing the productivity, a modification of adding a pre-twister and holding roller on the traditional ring spinning system have been discussed in this paper. The computational fluid dynamics (CFD) are introduced to study the effects of pre-twister and spinning tests are implemented for verification. The numerical simulations show that the cavity conical degree and nozzle numbers of the pre-twister are the key parameters which affect the airflow fluctuation in the cavity, and have obvious effects on the resultant yarn twist. By contrast, the axial angle and tangential angle of the nozzle have less effect on the resultant yarn twist. When the fiber bundles pass by the front nip, they are affected by the vortex and result in a partially strengthened and wrapped structure which could be subsequently twisted less by the traveler and ring, so the productivity could be potentially increased. According to the spinning tests, an evident productivity increase by nearly 30% for medium cotton yarns can be achieved, and the yarns have an acceptable reduction in nearly all properties. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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21 pages, 6038 KiB

Open AccessArticle

On the Mechanisms of the Effects of Ionizing Radiation on Diblock and Random Copolymers of Poly(Lactic Acid) and Poly(Trimethylene Carbonate)

by Agnieszka Adamus-Wlodarczyk, Radoslaw A. Wach, Piotr Ulanski, Janusz M. Rosiak, Marta Socka, Zois Tsinas and Mohamad Al-Sheikhly

Polymers 2018, 10(6), 672; https://doi.org/10.3390/polym10060672 - 16 Jun 2018

Cited by 21 | Viewed by 5954

Abstract

This article demonstrates that ionizing radiation induces simultaneous crosslinking and scission in poly(trimethylene carbonate-co-d-lactide) diblock and random copolymers. Copolymer films were electron-beam (EB) irradiated up to 300 kGy under anaerobic conditions and subsequently examined by evaluation of their structure [...] Read more.

This article demonstrates that ionizing radiation induces simultaneous crosslinking and scission in poly(trimethylene carbonate-co-d-lactide) diblock and random copolymers. Copolymer films were electron-beam (EB) irradiated up to 300 kGy under anaerobic conditions and subsequently examined by evaluation of their structure (FT-IR, NMR), molecular weight, intrinsic viscosities, and thermal properties. Radiation chemistry of the copolymers is strongly influenced by the content of ester linkages of the lactide component. At low lactide content, crosslinking reaction is the dominant one; however, as the lactide ratio increases, the ester linkages scission becomes more competent and exceeds the crosslinking. Electron paramagnetic resonance (EPR) measurements indicate that higher content of amorphous carbonate units in copolymers leads to a reduction in free radical yield and faster radical decay as compared to lactide-rich compositions. The domination of scission of ester bonds was confirmed by identifying the radiolytically produced alkoxyl and acetyl radicals, the latter being more stable due to its conjugated structure. Full article

(This article belongs to the Special Issue Radiation Effects in Polymers)

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13 pages, 2482 KiB

Open AccessArticle

Wound Dressings Based on Chitosan-Dialdehyde Cellulose Nanocrystals-Silver Nanoparticles: Mechanical Strength, Antibacterial Activity and Cytotoxicity

by Feng Dong and Shujun Li

Polymers 2018, 10(6), 673; https://doi.org/10.3390/polym10060673 - 16 Jun 2018

Cited by 57 | Viewed by 7136

Abstract

The present work envisages a simple approach to synthesize a new wound dressing based on chitosan-dialdehyde cellulose nanocrystal-silver nanoparticles (CS-DCNC-AgNPs). Silver nanoparticles (AgNPs) were generated in-situ by periodate oxidation of cellulose nanocrystals to generate aldehyde functions, which were used to reduce Ag⁺ [...] Read more.

The present work envisages a simple approach to synthesize a new wound dressing based on chitosan-dialdehyde cellulose nanocrystal-silver nanoparticles (CS-DCNC-AgNPs). Silver nanoparticles (AgNPs) were generated in-situ by periodate oxidation of cellulose nanocrystals to generate aldehyde functions, which were used to reduce Ag⁺ into Ag⁰ in mild alkaline conditions. Subsequently, the dialdehyde cellulose nanocrystal-silver nanoparticles (DCNC-AgNPs) were added to chitosan (CS) to form the wound dressings by solution casting method. The aim was to enhance the antibacterial effect of CS by incorporation of AgNPs and to improve the mechanical strength and hydrophobicity of CS by incorporation of DCNC that cross-linked by hydrogen bonds. The antibacterial activities were evaluated against five gram-negative bacteria, one gram-positive bacteria, and three fungi. The in vitro cytotoxicity assay was performed using the NIH3T3 cell lines by Sulforhodamine B assay. Research outputs signified that CS-DCNC-AgNPs possessed good mechanical strength and hydrophobicity, high antibacterial activity and less cytotoxicity. Our results propose that CS-DCNC-AgNPs can be a promising, safe antibacterial to be incorporated in wound dressings. Full article

(This article belongs to the Special Issue Polysaccharides)

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16 pages, 5699 KiB

Open AccessArticle

Polymer Optical Fiber Bragg Gratings in CYTOP Fibers for Angle Measurement with Dynamic Compensation

by Arnaldo Leal-Junior, Antreas Theodosiou, Camilo Díaz, Carlos Marques, Maria José Pontes, Kyriacos Kalli and Anselmo Frizera-Neto

Polymers 2018, 10(6), 674; https://doi.org/10.3390/polym10060674 - 17 Jun 2018

Cited by 83 | Viewed by 5434

Abstract

This paper demonstrates the use of polymer optical fiber Bragg gratings (POFBGs) for angle measurements over a range of different oscillatory frequencies. The POFBGs are inscribed in low-loss, cyclic transparent amorphous fluoropolymers (CYTOP) and are imprinted using the direct-write, plane-by-plane femtosecond laser inscription [...] Read more.

This paper demonstrates the use of polymer optical fiber Bragg gratings (POFBGs) for angle measurements over a range of different oscillatory frequencies. The POFBGs are inscribed in low-loss, cyclic transparent amorphous fluoropolymers (CYTOP) and are imprinted using the direct-write, plane-by-plane femtosecond laser inscription method. As the polymer has a viscoelastic response and given that the Young’s modulus depends on the oscillatory frequency, a compensation technique for sensor frequency cross-sensitivity and hysteresis is proposed and verified. Results show that the proposed compensation technique is able to provide a root mean squared error (RMSE) reduction of 44%, and a RMSE as low as 2.20° was obtained when compared with a reference potentiometer. The hysteresis reduction provided by the proposed technique is 55%, with hysteresis <0.01. The results presented in this paper can pave the way for movement analysis with POFBG providing higher sensitivity and low hysteresis over a large range of motion frequencies. Full article

(This article belongs to the Special Issue Holographic Materials and Photonic Applications)

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13 pages, 4032 KiB

Open AccessArticle

Effect of a Surfactant in Microcapsule Synthesis on Self-Healing Behavior of Capsule Embedded Polymeric Films

by Jiyeon Lee, Seon Joo Park, Chul-Soon Park, Oh Seok Kwon, So Young Chung, Jongwon Shim, Chang-Soo Lee and Joonwon Bae

Polymers 2018, 10(6), 675; https://doi.org/10.3390/polym10060675 - 17 Jun 2018

Cited by 15 | Viewed by 6374

Abstract

Recently, there has been increased interest in self-healing membranes containing functional microcapsules in relation to challenges involving water treatment membranes. In this study, a self-healing membrane has been prepared by incorporating microcapsules with a polyurethane (PU) shell and a diisocyanate core in a [...] Read more.

Recently, there has been increased interest in self-healing membranes containing functional microcapsules in relation to challenges involving water treatment membranes. In this study, a self-healing membrane has been prepared by incorporating microcapsules with a polyurethane (PU) shell and a diisocyanate core in a poly(ether sulfone) (PES) membrane. Depending on the characteristics of the microcapsule, to precisely quantify the self-healing behavior and performance of the produced microcapsule embedded membranes, it is important to understand the effect of a used surfactant on microcapsule synthesis. It is noteworthy that mixed surfactants have been employed to control and tailor the size and morphology of microcapsules during the synthetic process, and the surfactant system employed was one of the most dominant parameters for affecting the healing capability of microcapsule embedded membranes. Various techniques including microscopy (optical and electron), thermal analyses (DSC and TGA), and water flux measurements have been employed. This article provides essential and important information for future research into the subtle relation between microcapsule properties with varied synthetic parameters and the self-healing behavior of membrane. Full article

(This article belongs to the Special Issue Polymer Hybrid Materials)

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11 pages, 3012 KiB

Open AccessArticle

Critical Point Drying: An Effective Drying Method for Direct Measurement of the Surface Area of a Pretreated Cellulosic Biomass

by Kyu-Young Kang, Kyung-Ran Hwang, Ji-Yeon Park, Joon-Pyo Lee, Jun-Seok Kim and Jin-Suk Lee

Polymers 2018, 10(6), 676; https://doi.org/10.3390/polym10060676 - 17 Jun 2018

Cited by 27 | Viewed by 8215

Abstract

The surface area and pore size distribution of Eucalyptus samples that were pretreated by different methods were determined by the Brunauer–Emmett–Teller (BET) technique. Three methods were applied to prepare cellulosic biomass samples for the BET measurements, air, freeze, and critical point drying (CPD). [...] Read more.

The surface area and pore size distribution of Eucalyptus samples that were pretreated by different methods were determined by the Brunauer–Emmett–Teller (BET) technique. Three methods were applied to prepare cellulosic biomass samples for the BET measurements, air, freeze, and critical point drying (CPD). The air and freeze drying caused a severe collapse of the biomass pore structures, but the CPD effectively preserved the biomass morphology. The surface area of the CPD prepared Eucalyptus samples were determined to be 58–161 m²/g, whereas the air and freeze dried samples were 0.5–1.3 and 1.0–2.4 m²/g, respectively. The average pore diameter of the CPD prepared Eucalyptus samples were 61–70 Å. The CPD preserved the Eucalyptus sample morphology by replacing water with a non-polar solvent, CO₂ fluid, which prevented hydrogen bond reformation in the cellulose. Full article

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15 pages, 4223 KiB

Open AccessArticle

Preparation of Compositional Gradient Polymeric Films Based on Gradient Mesh Template

by Honglei Teng, Jing Li, Zhaosheng Hou, Xilu Yan, Linru Han, Jing Xu and Tianduo Li

Polymers 2018, 10(6), 677; https://doi.org/10.3390/polym10060677 - 18 Jun 2018

Cited by 7 | Viewed by 4422

Abstract

In this paper, a template-filling method was found to prepare composition gradient gelatin films by incorporating α-[3-(2,3-epoxypropoxy) propyl]-ω-butyl-polydimethylsiloxane (PDMS–E) grafted gelatin (PGG) into a gradient gelatin mesh template. The method can be used to prepare other composition gradient biopolymer films. Gradient mesh template [...] Read more.

In this paper, a template-filling method was found to prepare composition gradient gelatin films by incorporating α-[3-(2,3-epoxypropoxy) propyl]-ω-butyl-polydimethylsiloxane (PDMS–E) grafted gelatin (PGG) into a gradient gelatin mesh template. The method can be used to prepare other composition gradient biopolymer films. Gradient mesh template prepared by the methacrylic anhydride cross-linked gelatin under temperature gradient field. The porosity of the template decreased from 89 to 35% which was accompanied by decrease in average pore size from 160 to 50 µm. Colloidal particles about 0.9~10 µm were formed from PGG after adding them to a mixed solvent system of 9:1 (v/v) of ethanol/water, which were filled in the mesh template under vacuum (0.06 MPa). A gradient film was obtained after drying at room temperature for 48 h. The results of scanning electron microscope-energy dispersive X-ray combined with freezing microtome and Fourier transform infrared spectroscopy suggested that the distribution of the Si element along the thickness showed a typical gradient pattern, which led to hydrophilic/hydrophobic continuous changing along the thickness of film. The water vapor permeability, thermal gravimetric analysis, differential scanning calorimetry and dynamic mechanical tensile results show that the gradient films had excellent water vapor permeability and flexibility, and hence could be used as biomimetic materials and leather finishing agents. Full article

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23 pages, 44886 KiB

Open AccessArticle

Finite-Element Investigation of the Structural Behavior of Basalt Fiber Reinforced Polymer (BFRP)- Reinforced Self-Compacting Concrete (SCC) Decks Slabs in Thompson Bridge

by Lingzhu Zhou, Yu Zheng and Susan E. Taylor

Polymers 2018, 10(6), 678; https://doi.org/10.3390/polym10060678 - 18 Jun 2018

Cited by 18 | Viewed by 4814

Abstract

The need for a sustainable development and improved whole life performance of concrete infrastructure has led to the requirement of more durable and sustainable concrete bridges alongside accurate predictive analysis tools. Using the combination of Self-Compacting Concrete (SCC) with industrial by-products and fiber-reinforced [...] Read more.

The need for a sustainable development and improved whole life performance of concrete infrastructure has led to the requirement of more durable and sustainable concrete bridges alongside accurate predictive analysis tools. Using the combination of Self-Compacting Concrete (SCC) with industrial by-products and fiber-reinforced polymer (FRP), reinforcement is anticipated to address the concerns of high carbon footprint and corrosion in traditional steel-reinforced concrete structures. This paper presents a numerical investigation of the structural behavior of basalt fiber-reinforced polymer (BFRP)-reinforced SCC deck slabs in a real bridge, named Thompson Bridge, constructed in Northern Ireland, U.K. A non-linear finite element (FE) model is proposed by using ABAQUS 6.10 in this study, which is aimed at extending the previous investigation of the field test in Thompson Bridge. The results of this field test were used to validate the accuracy of the proposed finite element model. The results showed good agreement between the test results and the numerical results; more importantly, the compressive membrane action (CMA) inside the slabs could be well demonstrated by this FE model. Subsequently, a series of parametric studies was conducted to investigate the influence of different parameters on the structural performance of the deck slabs in Thompson Bridge. The results of the analyses are discussed, and conclusions on the behavior of the SCC deck slabs reinforced by BFRP bars are presented. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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16 pages, 10229 KiB

Open AccessArticle

Molecularly Imprinted Polymers for the Selective Extraction of Bisphenol A and Progesterone from Aqueous Media

by César Cáceres, Catalina Bravo, Bernabé Rivas, Ewa Moczko, Pedro Sáez, Yadiris García and Eduardo Pereira

Polymers 2018, 10(6), 679; https://doi.org/10.3390/polym10060679 - 19 Jun 2018

Cited by 29 | Viewed by 5790

Abstract

This paper describes the development of a novel sorbent for selective extraction of endocrine disruptors (EDs) from aqueous media. The main goal was to obtain sufficient molecularly imprinted polymers (MIPs) for selective detection, preconcentration, and extraction of EDs such as bisphenol A (BPA) [...] Read more.

This paper describes the development of a novel sorbent for selective extraction of endocrine disruptors (EDs) from aqueous media. The main goal was to obtain sufficient molecularly imprinted polymers (MIPs) for selective detection, preconcentration, and extraction of EDs such as bisphenol A (BPA) and progesterone (PG). Series of MIPs and their analogues, non-molecularly imprinted polymers (NIPs), were synthesised following a non-covalent imprinting strategy based on radical polymerisation. Sets of synthesis were performed in order to optimise variables of the polymerisation including solvent, cross-linker, and template ratio. The retention capacity of MIPs was determined using HPLC in the range of 33.3% to 96.6% and 32.5% to 96% for BPA and PG, respectively. The adsorption mechanism was studied by isothermal and kinetic assays. The kinetic analysis showed a high retention capacity within 15 min of contact. The polymer yield was obtained in the range of 30% to 100%. Additionally, there was no significant cross-reactivity observed upon testing MIPs with structural analogues and other endocrine disruptors instead of target molecules. The results also revealed the high importance of different concentrations of cross-linker and solvent during the polymerisation. Firstly, the pre-organisation of complementary functional groups, which were present in the polymerisation mixture, and secondly, selective cavity formation for target molecules. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers)

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14 pages, 3345 KiB

Open AccessArticle

Centrifugally Spun Recycled PET: Processing and Characterization

by Phu Phong Vo, Hoan Ngoc Doan, Kenji Kinashi, Wataru Sakai, Naoto Tsutsumi and Dai Phu Huynh

Polymers 2018, 10(6), 680; https://doi.org/10.3390/polym10060680 - 19 Jun 2018

Cited by 39 | Viewed by 7871

Abstract

Centrifugal spinning, which is a high-productivity fiber fabrication technique, was used to produce a value-added product from recycled poly(ethylene terephthalate) (rPET). In the present study, rPET fibers, with fiber diameters ranging from submicron to micrometer in scale, were fabricated by spinning a solution [...] Read more.

Centrifugal spinning, which is a high-productivity fiber fabrication technique, was used to produce a value-added product from recycled poly(ethylene terephthalate) (rPET). In the present study, rPET fibers, with fiber diameters ranging from submicron to micrometer in scale, were fabricated by spinning a solution of rPET in a mixture of dichloromethane and trifluoroacetic acid. The influence of the polymer solution concentration (the viscosity), the rotational speed of the spinneret, and the inner diameter of the needles on the formation and morphology and mechanical properties of the fibers were examined through scanning electron microscopy and using a tensile testing machine. The thermal behaviors of fibrous mats with various average diameters were also investigated through differential scanning calorimetry. The smoothest and smallest fibers, with an average diameter of 619 nm, were generated using an rPET solution of 10 wt % under a rotation speed of 15,000 rpm using needles having an inner diameter of 160 μm. The fibrous mats have an average tensile strength and modulus of 4.3 MPa and 34.4 MPa, respectively. The productivity and the mechanical properties indicate that centrifugal spinning is an effective technique to fabricate high-value product from rPET. Full article

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13 pages, 4089 KiB

Open AccessArticle

Fabric Coated with Shape Memory Polyurethane and Its Properties

by Md Anwar Jahid, Jinlian Hu, KwanHa Wong, You Wu, Yong Zhu, Hogan Hong Sheng Luo and Deng Zhongmin

Polymers 2018, 10(6), 681; https://doi.org/10.3390/polym10060681 - 19 Jun 2018

Cited by 51 | Viewed by 9483

Abstract

In order to provide thermo-physiological comfort to the wearer, textile materials should have some functional property like water-resistance or water vapor transmission (WVT), so that perspiration can evaporate and be transmitted from the body surface to the environment even in extreme weather conditions [...] Read more.

In order to provide thermo-physiological comfort to the wearer, textile materials should have some functional property like water-resistance or water vapor transmission (WVT), so that perspiration can evaporate and be transmitted from the body surface to the environment even in extreme weather conditions that require wind and rain proof. Shape memory polyurethane (SMPU) could possibly be a candidate; it is a functional textile material that meets such requirements. In this research, we synthesized a series of SMPUs, which are responsive materials, to test whether these coated cotton fabrics could provide thermal insulation with lower permeability at low temperature or low relative humidity (RH), and high permeability at room temperature or above, or high relative humidity with its water-resistance property. In this paper, we have proposed a segmented shape memory polyurethane for coated textiles in order to have a water-resistant textile with good water vapor transmitting ability. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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12 pages, 2476 KiB

Open AccessArticle

Sol-Gel Synthesis, Spectroscopic and Thermal Behavior Study of SiO₂/PEG Composites Containing Different Amount of Chlorogenic Acid

by Michelina Catauro, Elisabetta Tranquillo, Roberta Risoluti and Stefano Vecchio Ciprioti

Polymers 2018, 10(6), 682; https://doi.org/10.3390/polym10060682 - 19 Jun 2018

Cited by 56 | Viewed by 6222

Abstract

In this work, new phenol-based materials have been synthesized by the sol-gel method, in which different amounts of the phenolic antioxidant chlorogenic acid (CGA) (from 5 wt % to 20 wt %) were embedded in two different silica matrices: pure silica and silica-based [...] Read more.

In this work, new phenol-based materials have been synthesized by the sol-gel method, in which different amounts of the phenolic antioxidant chlorogenic acid (CGA) (from 5 wt % to 20 wt %) were embedded in two different silica matrices: pure silica and silica-based hybrids materials, containing 50 wt % of polyethylene glycol (PEG). The incorporation of CGA in different sol-gel matrices might protect them from degradation, which could cause the loss of their properties. The two series of materials were chemically characterized by Fourier transform infrared (FTIR) spectroscopy. In addition, the thermal behavior of both series of materials containing CGA was studied by thermogravimetry under both air and inert N₂ flowing gas atmosphere. The bioactivity was evaluated by soaking the synthesized hybrids in a simulated body fluid, showing that the bioactivity of the silica matrix is not modified by the presence of PEG and CGA. Full article

(This article belongs to the Special Issue Siloxane-Based Polymers)

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15 pages, 2568 KiB

Open AccessArticle

An Analytical Model of Interlaminar Fracture of Polymer Composite Reinforced by Carbon Fibres Grafted with Carbon Nanotubes

by Feng Xu, Hong-Yuan Liu and Xusheng Du

Polymers 2018, 10(6), 683; https://doi.org/10.3390/polym10060683 - 19 Jun 2018

Cited by 24 | Viewed by 3633

Abstract

An analytical model was developed to study the interlaminar fracture behaviour of polymer composite reinforced by carbon fibres grafted with carbon nanotubes. Delamination properties, such as load with displacement or crack (R-curve) and toughness with crack (G_R-curve), can [...] Read more.

An analytical model was developed to study the interlaminar fracture behaviour of polymer composite reinforced by carbon fibres grafted with carbon nanotubes. Delamination properties, such as load with displacement or crack (R-curve) and toughness with crack (G_R-curve), can be obtained from this model. The bridging laws presented, based on the CNT pullout mechanism (CNT pullout from polymer matrix) and the CNT sword-in-sheath mechanism (CNT breakage), were incorporated into the proposed analytical model to investigate the influence of the structure of CNT growth onto CFs (CNT@CFs) on delamination properties. The numerical results showed that different toughening mechanisms led to different features of G_R-curves, R-curves, and load with displacement curves. Parametric study demonstrated that strengthening the CNT@CF interface resulted in significant improvement in toughness. Further, it was found that elastic deformation of CNTs played an important role in the toughness improvement in the CNT sword-in-sheath mechanism, but no such role was evident in the CNT pullout mechanism. Full article

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13 pages, 811 KiB

Open AccessArticle

Analysis of the Models of Motion of Aqueous Solutions of Polymers on the Basis of Their Exact Solutions

by Oxana A. Frolovskaya and Vladislav V. Pukhnachev

Polymers 2018, 10(6), 684; https://doi.org/10.3390/polym10060684 - 19 Jun 2018

Cited by 19 | Viewed by 3714

Abstract

The qualitative properties of solutions of a hereditary model of motion of aqueous solutions of polymers, its modification in the limiting case of short relaxation times, and a similar second grade fluid model are studied. Unsteady shear flows are considered. In the first [...] Read more.

The qualitative properties of solutions of a hereditary model of motion of aqueous solutions of polymers, its modification in the limiting case of short relaxation times, and a similar second grade fluid model are studied. Unsteady shear flows are considered. In the first case, their properties are similar to those of motion of a usual viscous fluid. Other models can include weak discontinuities, which are retained in the course of fluid motion. Exact solutions are found by using the group analysis of the examined systems of equations. These solutions describe the fluid motion in a gap between coaxial rotating cylinders, the stagnation point flow, and the motion in a half-space induced by plane rotation (analog of the Karman vortex). The problem of motion of an aqueous solution of a polymer in a cylindrical tube under the action of a streamwise pressure gradient is considered. In this case, a flow with straight-line trajectories is possible (analog of the Hagen-Poiseuille flow). In contrast to the latter, however, the pressure in the flow considered here depends on all three spatial variables. Full article

(This article belongs to the Special Issue Polymer Dynamics)

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15 pages, 5677 KiB

Open AccessArticle

Modification of PSf/SPSf Blended Porous Support for Improving the Reverse Osmosis Performance of Aromatic Polyamide Thin Film Composite Membranes

by Li-Fen Liu, Xing-Ling Gu, Xin Xie, Rui-Han Li, Chun-Yang Yu, Xiao-Xiao Song and Cong-Jie Gao

Polymers 2018, 10(6), 686; https://doi.org/10.3390/polym10060686 - 20 Jun 2018

Cited by 24 | Viewed by 7167

Abstract

In this study, modification of polysulfone (PSf)/sulfonated polysulfone (SPSf) blended porous ultrafiltration (UF) support membranes was proposed to improve the reverse osmosis (RO) performance of aromatic polyamide thin film composite (TFC) membranes. The synergistic effects of solvent, polymer concentration, and SPSf doping content [...] Read more.

In this study, modification of polysulfone (PSf)/sulfonated polysulfone (SPSf) blended porous ultrafiltration (UF) support membranes was proposed to improve the reverse osmosis (RO) performance of aromatic polyamide thin film composite (TFC) membranes. The synergistic effects of solvent, polymer concentration, and SPSf doping content in the casting solution were investigated systematically on the properties of both porous supports and RO membranes. SEM and AFM were combined to characterize the physical properties of the membranes, including surface pore natures (porosity, mean pore radius), surface morphology, and section structure. A contact angle meter was used to analyze the membrane surface hydrophilicity. Permeate experiments were carried out to evaluate the separation performances of the membranes. The results showed that the PSf/SPSf blended porous support modified with 6 wt % SPSf in the presence of DMF and 14 wt % PSf had higher porosity, bigger pore diameter, and a rougher and more hydrophilic surface, which was more beneficial for fabrication of a polyamide TFC membrane with favorable reverse osmosis performance. This modified PSf/SPSf support endowed the RO membrane with a more hydrophilic surface, higher water flux (about 1.2 times), as well as a slight increase in salt rejection than the nascent PSf support. In a word, this work provides a new facile method to improve the separation performance of polyamide TFC RO membranes via the modification of conventional PSf porous support with SPSf. Full article

(This article belongs to the Special Issue Aromatic Polymers)

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14 pages, 2147 KiB

Open AccessArticle

Modular Synthesis of Bioreducible Gene Vectors through Polyaddition of N,N′-Dimethylcystamine and Diglycidyl Ethers

by Guoying Si, M. Rachèl Elzes, Johan F. J. Engbersen and Jos M. J. Paulusse

Polymers 2018, 10(6), 687; https://doi.org/10.3390/polym10060687 - 20 Jun 2018

Cited by 7 | Viewed by 4858

Abstract

Bioreducible, cationic linear poly(amino ether)s (PAEs) were designed as promising gene vectors. These polymers were synthesized by the reaction of a disulfide-functional monomer, N,N′-dimethylcystamine (DMC), and several different diglycidyl ethers. The resulting PAEs displayed a substantial buffer capacity (up to [...] Read more.

Bioreducible, cationic linear poly(amino ether)s (PAEs) were designed as promising gene vectors. These polymers were synthesized by the reaction of a disulfide-functional monomer, N,N′-dimethylcystamine (DMC), and several different diglycidyl ethers. The resulting PAEs displayed a substantial buffer capacity (up to 64%) in the endosomal acidification region of pH 7.4–5.1. The PAEs condense plasmid DNA into 80–200 nm sized polyplexes, and have surface charges ranging from +20 to +40 mV. The polyplexes readily release DNA upon exposure to reducing conditions (2.5 mM DTT) due to the cleavage of the disulfide groups that is present in the main chain of the polymers, as was demonstrated by agarose gel electrophoresis. Upon exposing COS-7 cells to polyplexes that were prepared at polymer/DNA w/w ratios below 48, cell viabilities between 80–100% were observed, even under serum-free conditions. These polyplexes show comparable or higher transfection efficiencies (up to 38%) compared to 25 kDa branched polyethylenimine (PEI) polyplexes (12% under serum-free conditions). Moreover, the PAE-based polyplexes yield transfection efficiencies as high as 32% in serum-containing medium, which makes these polymers interesting for gene delivery applications. Full article

(This article belongs to the Special Issue Polymers in Gene Delivery)

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18 pages, 12522 KiB

Open AccessArticle

Enzymatic Degradation of Poly(butylene succinate) Copolyesters Synthesized with the Use of Candida antarctica Lipase B

by Aleksandra Wcisłek, Agueda Sonseca Olalla, Andrew McClain, Agnieszka Piegat, Peter Sobolewski, Judit Puskas and Miroslawa El Fray

Polymers 2018, 10(6), 688; https://doi.org/10.3390/polym10060688 - 20 Jun 2018

Cited by 37 | Viewed by 6897

Abstract

Biodegradable polymers are an active area of investigation, particularly ones that can be produced from sustainable, biobased monomers, such as copolymers of poly(butylene succinate) (PBS). In this study, we examine the enzymatic degradation of poly(butylene succinate-dilinoleic succinate) (PBS-DLS) copolymers obtained by “green” enzymatic [...] Read more.

Biodegradable polymers are an active area of investigation, particularly ones that can be produced from sustainable, biobased monomers, such as copolymers of poly(butylene succinate) (PBS). In this study, we examine the enzymatic degradation of poly(butylene succinate-dilinoleic succinate) (PBS-DLS) copolymers obtained by “green” enzymatic synthesis using lipase B from Candida antarctica (CALB). The copolymers differed in their hard to soft segments ratio, from 70:30 to 50:50 wt %. Enzymatic degradation was carried out on electrospun membranes (scaffolds) and compression-moulded films using lipase from Pseudomomas cepacia. Poly(ε-caprolactone) (PCL) was used as a reference aliphatic polyester. The degradation process was monitored gravimetrically via water uptake and mass loss. After 24 days, approx. 40% mass loss was observed for fibrous materials prepared from the PBS-DLS 70:30 copolymer, as compared to approx. 10% mass loss for PBS-DLS 50:50. Infrared spectroscopy (FTIR) and size exclusion chromatography (SEC) analysis were used to examine changes in chemical structure. Differential scanning calorimetry (DSC) and scanning light microscopy (LSM) revealed changes in degree of crystallinity, and changes in surface morphology, consistent with a surface erosion mechanism. We conclude that the obtained copolymers are suitable for tissue engineering applications thanks to tuneable degradation and lack of acidification during breakdown. Full article

(This article belongs to the Special Issue Biodegradable and Biobased Polyesters)

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21 pages, 2042 KiB

Open AccessArticle

Efficient Shielding of Polyplexes Using Heterotelechelic Polysarcosines

by Philipp Michael Klein, Kristina Klinker, Wei Zhang, Sarah Kern, Eva Kessel, Ernst Wagner and Matthias Barz

Polymers 2018, 10(6), 689; https://doi.org/10.3390/polym10060689 - 20 Jun 2018

Cited by 23 | Viewed by 7815

Abstract

Shielding agents are commonly used to shield polyelectrolyte complexes, e.g., polyplexes, from agglomeration and precipitation in complex media like blood, and thus enhance their in vivo circulation times. Since up to now primarily poly(ethylene glycol) (PEG) has been investigated to shield non-viral carriers [...] Read more.

Shielding agents are commonly used to shield polyelectrolyte complexes, e.g., polyplexes, from agglomeration and precipitation in complex media like blood, and thus enhance their in vivo circulation times. Since up to now primarily poly(ethylene glycol) (PEG) has been investigated to shield non-viral carriers for systemic delivery, we report on the use of polysarcosine (pSar) as a potential alternative for steric stabilization. A redox-sensitive, cationizable lipo-oligomer structure (containing two cholanic acids attached via a bioreducible disulfide linker to an oligoaminoamide backbone in T-shape configuration) was equipped with azide-functionality by solid phase supported synthesis. After mixing with small interfering RNA (siRNA), lipopolyplexes formed spontaneously and were further surface-functionalized with polysarcosines. Polysarcosine was synthesized by living controlled ring-opening polymerization using an azide-reactive dibenzo-aza-cyclooctyne-amine as an initiator. The shielding ability of the resulting formulations was investigated with biophysical assays and by near-infrared fluorescence bioimaging in mice. The modification of ~100 nm lipopolyplexes was only slightly increased upon functionalization. Cellular uptake into cells was strongly reduced by the pSar shielding. Moreover, polysarcosine-shielded polyplexes showed enhanced blood circulation times in bioimaging studies compared to unshielded polyplexes and similar to PEG-shielded polyplexes. Therefore, polysarcosine is a promising alternative for the shielding of non-viral, lipo-cationic polyplexes. Full article

(This article belongs to the Special Issue Hydrophilic Polymers)

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Review

Jump to: Research, Other

18 pages, 10031 KiB

Open AccessReview

Polymer Interface Molecular Engineering for E-Textiles

by Chuang Zhu, Yi Li and Xuqing Liu

Polymers 2018, 10(6), 573; https://doi.org/10.3390/polym10060573 - 23 May 2018

Cited by 27 | Viewed by 7924

Abstract

Wearable electronics, regarded as the next generation of conventional textiles, have been an important concept in the study of e-textiles. Conductive fibres are the upstreaming of e-textiles and have witnessed the booming development in recent years. However, little work has focused on improving [...] Read more.

Wearable electronics, regarded as the next generation of conventional textiles, have been an important concept in the study of e-textiles. Conductive fibres are the upstreaming of e-textiles and have witnessed the booming development in recent years. However, little work has focused on improving the wash ability and durability of conductive fibres. As a new approach to manufacturing conductive fibres, Polymer Interface Molecular Engineering (PIME) is starting to be employed recently, to build up an interfacial layer on polymeric fibre surfaces; this interfacial layer services as a platform to anchor catalysts for the following metal Electroless Deposition (ELD). The designed interfacial layer significantly increases adhesion between polymeric substrates and coating metal layers, to improve the durability of e-textiles. This review highlights recent research into different molecular and architectural design strategies, and its potential application for wearable electronics. Further challenges and opportunities in this field are also discussed critically. Full article

(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)

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11 pages, 1317 KiB

Open AccessReview

Dendritic Polyglycerol Sulfate for Therapy and Diagnostics

by Nadine Rades, Kai Licha and Rainer Haag

Polymers 2018, 10(6), 595; https://doi.org/10.3390/polym10060595 - 29 May 2018

Cited by 22 | Viewed by 6683

Abstract

Dendritic polyglycerol sulfate (dPGS) has originally been investigated as an anticoagulant to potentially substitute for the natural glycosaminoglycan heparin. Compared to unfractionated heparin, dPGS possesses lower anticoagulant activity but a much higher anticomplementary effect. Since coagulation, complement activation, and inflammation are often present [...] Read more.

Dendritic polyglycerol sulfate (dPGS) has originally been investigated as an anticoagulant to potentially substitute for the natural glycosaminoglycan heparin. Compared to unfractionated heparin, dPGS possesses lower anticoagulant activity but a much higher anticomplementary effect. Since coagulation, complement activation, and inflammation are often present in the pathophysiology of numerous diseases, dPGS polymers with both anticoagulant and anticomplementary activities represent promising candidates for the development of polymeric drugs of nanosized architecture. In this review, we describe the nanomedical applications of dPGS based on its anti-inflammatory activity. Furthermore, the application of dPGS as a carrier molecule for diagnostic molecules and therapeutic drugs is reviewed, based on the ability to target tumors and localize in tumor cells. Finally, the application of dPGS for inhibition of virus infections is described. Full article

(This article belongs to the Special Issue Polymers for Therapy and Diagnostics)

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28 pages, 12165 KiB

Open AccessReview

Recent Progress of Imprinted Polymer Photonic Waveguide Devices and Applications

by Xiu-You Han, Zhen-Lin Wu, Si-Cheng Yang, Fang-Fang Shen, Yu-Xin Liang, Ling-Hua Wang, Jin-Yan Wang, Jun Ren, Ling-Yun Jia, Hua Zhang, Shu-Hui Bo, Geert Morthier and Ming-Shan Zhao

Polymers 2018, 10(6), 603; https://doi.org/10.3390/polym10060603 - 31 May 2018

Cited by 38 | Viewed by 9234

Abstract

Polymers are promising materials for fabricating photonic integrated waveguide devices. Versatile functional devices can be manufactured using a simple process, with low cost and potential mass-manufacturing. This paper reviews the recent progress of polymer photonic integrated devices fabricated using the UV imprinting technique. [...] Read more.

Polymers are promising materials for fabricating photonic integrated waveguide devices. Versatile functional devices can be manufactured using a simple process, with low cost and potential mass-manufacturing. This paper reviews the recent progress of polymer photonic integrated devices fabricated using the UV imprinting technique. The passive polymer waveguide devices for wavelength filtering, power splitting, and light collecting, and the active polymer waveguide devices based on the thermal-optic tuning effect, are introduced. Then, the electro-optic (EO) modulators, by virtue of the high EO coefficient of polymers, are described. Finally, the photonic biosensors, which are based on low-cost and biocompatible polymer platforms, are presented. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers)

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28 pages, 732 KiB

Open AccessReview

Cellulose Aerogels: Synthesis, Applications, and Prospects

by Lin-Yu Long, Yun-Xuan Weng and Yu-Zhong Wang

Polymers 2018, 10(6), 623; https://doi.org/10.3390/polym10060623 - 6 Jun 2018

Cited by 464 | Viewed by 35901

Abstract

Due to its excellent performance, aerogel is considered to be an especially promising new material. Cellulose is a renewable and biodegradable natural polymer. Aerogel prepared using cellulose has the renewability, biocompatibility, and biodegradability of cellulose, while also having other advantages, such as low [...] Read more.

Due to its excellent performance, aerogel is considered to be an especially promising new material. Cellulose is a renewable and biodegradable natural polymer. Aerogel prepared using cellulose has the renewability, biocompatibility, and biodegradability of cellulose, while also having other advantages, such as low density, high porosity, and a large specific surface area. Thus, it can be applied for many purposes in the areas of adsorption and oil/water separation, thermal insulation, and biomedical applications, as well as many other fields. There are three types of cellulose aerogels: natural cellulose aerogels (nanocellulose aerogels and bacterial cellulose aerogels), regenerated cellulose aerogels, and aerogels made from cellulose derivatives. In this paper, more than 200 articles were reviewed to summarize the properties of these three types of cellulose aerogels, as well as the technologies used in their preparation, such as the sol–gel process and gel drying. In addition, the applications of different types of cellulose aerogels were also introduced. Full article

(This article belongs to the Collection Polysaccharides)

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31 pages, 6317 KiB

Open AccessReview

3D Printing Technologies for Flexible Tactile Sensors toward Wearable Electronics and Electronic Skin

by Changyong Liu, Ninggui Huang, Feng Xu, Junda Tong, Zhangwei Chen, Xuchun Gui, Yuelong Fu and Changshi Lao

Polymers 2018, 10(6), 629; https://doi.org/10.3390/polym10060629 - 7 Jun 2018

Cited by 250 | Viewed by 25332

Abstract

3D printing has attracted a lot of attention in recent years. Over the past three decades, various 3D printing technologies have been developed including photopolymerization-based, materials extrusion-based, sheet lamination-based, binder jetting-based, power bed fusion-based and direct energy deposition-based processes. 3D printing offers unparalleled [...] Read more.

3D printing has attracted a lot of attention in recent years. Over the past three decades, various 3D printing technologies have been developed including photopolymerization-based, materials extrusion-based, sheet lamination-based, binder jetting-based, power bed fusion-based and direct energy deposition-based processes. 3D printing offers unparalleled flexibility and simplicity in the fabrication of highly complex 3D objects. Tactile sensors that emulate human tactile perceptions are used to translate mechanical signals such as force, pressure, strain, shear, torsion, bend, vibration, etc. into electrical signals and play a crucial role toward the realization of wearable electronics and electronic skin. To date, many types of 3D printing technologies have been applied in the manufacturing of various types of tactile sensors including piezoresistive, capacitive and piezoelectric sensors. This review attempts to summarize the current state-of-the-art 3D printing technologies and their applications in tactile sensors for wearable electronics and electronic skin. The applications are categorized into five aspects: 3D-printed molds for microstructuring substrate, electrodes and sensing element; 3D-printed flexible sensor substrate and sensor body for tactile sensors; 3D-printed sensing element; 3D-printed flexible and stretchable electrodes for tactile sensors; and fully 3D-printed tactile sensors. Latest advances in the fabrication of tactile sensors by 3D printing are reviewed and the advantages and limitations of various 3D printing technologies and printable materials are discussed. Finally, future development of 3D-printed tactile sensors is discussed. Full article

(This article belongs to the Special Issue Polymer-Based Flexible Printed Electronics and Sensors)

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12 pages, 1849 KiB

Open AccessReview

Recent Advances on Octahedral Polypyridyl Ruthenium(II) Complexes as Antimicrobial Agents

by Yulin Yang, Guojian Liao and Chen Fu

Polymers 2018, 10(6), 650; https://doi.org/10.3390/polym10060650 - 10 Jun 2018

Cited by 41 | Viewed by 6284

Abstract

Recent developments of therapeutic agents based on transition metals have attracted a great deal of attention. Metal drugs have advantages over other small molecule drugs, and it was demonstrated that, in a number of studies, they played an important role in pharmaceutical chemical [...] Read more.

Recent developments of therapeutic agents based on transition metals have attracted a great deal of attention. Metal drugs have advantages over other small molecule drugs, and it was demonstrated that, in a number of studies, they played an important role in pharmaceutical chemical research and clinical chemotherapy of cancers. It is worthwhile mentioning that octahedral polypyridyl ruthenium(II) complexes have shown remarkable applications in chemical biology and medicinal chemistry over the last decade. However, only very recently has there been comprehensive interest in their antimicrobial properties due to metal-related toxic concerns or neglected potential roles in microbiological systems. Our review will highlight the recent developments in octahedral polypyridyl ruthenium(III) complexes that have exhibited significant antimicrobial activities and will discuss the relationship between the chemical structure and biological process of ruthenium complexes, in both bacterial and fungal cells. Full article

(This article belongs to the Special Issue Antimicrobial Polymers)

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19 pages, 1332 KiB

Open AccessReview

Compression Garments for Medical Therapy and Sports

by Ying Xiong and Xiaoming Tao

Polymers 2018, 10(6), 663; https://doi.org/10.3390/polym10060663 - 14 Jun 2018

Cited by 121 | Viewed by 20340

Abstract

Compression garments are elastic clothing with an engineered compression gradient that can be worn on limbs, upper, lower, or full body to use for therapy and sports. This article presents an overview and review on the compression garments and concentrates on the design [...] Read more.

Compression garments are elastic clothing with an engineered compression gradient that can be worn on limbs, upper, lower, or full body to use for therapy and sports. This article presents an overview and review on the compression garments and concentrates on the design of compression garments with an appropriate pressure for specific applications. It covers the types of compression garments, fibers and yarns, knitted fabric construction, garment design, an evaluation system, and pressure measurement and modeling. The material properties, fabric properties, pressure modeling, and the garment design system presents the prediction, design, and fabrication of the compression garments. Lastly, the research status and directions are discussed. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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14 pages, 5763 KiB

Open AccessReview

A Radio-Fluorogenic Polymer-Gel Makes Fixed Fluorescent Images of Complex Radiation Fields

by John M. Warman, Matthijs P. De Haas, Leonard H. Luthjens, Antonia G. Denkova and Tiantian Yao

Polymers 2018, 10(6), 685; https://doi.org/10.3390/polym10060685 - 20 Jun 2018

Cited by 10 | Viewed by 3916

Abstract

We review the development and application of an organic polymer-gel capable of producing fixed, three-dimensional fluorescent images of complex radiation fields. The gel consists for more than 99% of γ-ray-polymerized (~15% conversion) tertiary-butyl acrylate (TBA) containing ~100 ppm of a fluorogenic compound, e.g., [...] Read more.

We review the development and application of an organic polymer-gel capable of producing fixed, three-dimensional fluorescent images of complex radiation fields. The gel consists for more than 99% of γ-ray-polymerized (~15% conversion) tertiary-butyl acrylate (TBA) containing ~100 ppm of a fluorogenic compound, e.g., maleimido-pyrene (MPy). The radio-fluorogenic effect depends on copolymerization of the MPy into growing chains of TBA on radiation-induced polymerization. This converts the maleimido residue, which quenches the pyrene fluorescence, into a succinimido moeity (SPy), which does not. The intensity of the fluorescence is proportional to the yield of free-radicals formed and hence to the local dose deposited. Because the SPy moieties are built into the polymer network, the image is fixed. The method of preparing the gel and imaging the radiation-induced fluorescence are presented and discussed. The effect is illustrated with fluorescent images of the energy deposited in the gel by beams of X-rays, electrons, and protons as well as a radioactive isotope. Full article

(This article belongs to the Special Issue Polymer Characterization)

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