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Polymers, Volume 10, Issue 5 (May 2018)

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Cover Story (view full-size image) This work investigated the synthesis of novel chitosan-g-poly(methyl methacrylate) (CS-g-PMMA) [...] Read more.
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Open AccessArticle Love Wave Sensor for Prostate-Specific Membrane Antigen Detection Based on Hydrophilic Molecularly-Imprinted Polymer
Polymers 2018, 10(5), 563; https://doi.org/10.3390/polym10050563
Received: 20 April 2018 / Revised: 19 May 2018 / Accepted: 21 May 2018 / Published: 22 May 2018
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Abstract
Prostate-specific membrane antigen (PSMA) is a biomarker for prostate cancer (PCa), and a specific and reliable detection technique of PSMA is urgently required for PCa early diagnosis. A Love wave sensor has been widely studied for real-time sensing and highly sensitive applications, but
[...] Read more.
Prostate-specific membrane antigen (PSMA) is a biomarker for prostate cancer (PCa), and a specific and reliable detection technique of PSMA is urgently required for PCa early diagnosis. A Love wave sensor has been widely studied for real-time sensing and highly sensitive applications, but the sensing unit needs special handling for selective detection purpose. In this study, we prepared a versatile Love wave sensor functionalized with molecularly-imprinted polymers (MIP), PSMA as the template molecule. To enhance the specific template bindings of MIP in pure aqueous solutions, facile reversible addition/fragmentation chain transfer (RAFT) precipitation polymerization (RAFTPP) was used to produce surface hydrophilic polymer brushes on MIP. The presence of hydrophilic polymer brushes on MIP improved its surface hydrophilicity and significantly reduced their hydrophobic interactions with template molecules in pure aqueous media. In detection process, the acoustic delay-line is confederative to a microfluidic chip and inserted in an oscillation loop. The real-time resonance frequency of the MIP-based Love wave sensor to different concentrations of PSMA was investigated. The limit of detection (LOD) for this Love SAW sensor was 0.013 ng mL−1, which demonstrates that this sensor has outstanding performance in terms of the level of detection. Full article
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Open AccessArticle Ionic Liquids Incorporating Polyamide 6: Miscibility and Physical Properties
Polymers 2018, 10(5), 562; https://doi.org/10.3390/polym10050562
Received: 23 April 2018 / Revised: 10 May 2018 / Accepted: 17 May 2018 / Published: 22 May 2018
Cited by 1 | Viewed by 828 | PDF Full-text (4949 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The effects of 1-vinyl-3-butyl imidazole chloride (VBIM) on the structure and properties of Polyamide 6 (PA6) were investigated systematically. It was found that PA6/VBIM blends were homogeneous without phase separation. The glass transition temperature (Tg) of PA6 increased with small
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The effects of 1-vinyl-3-butyl imidazole chloride (VBIM) on the structure and properties of Polyamide 6 (PA6) were investigated systematically. It was found that PA6/VBIM blends were homogeneous without phase separation. The glass transition temperature (Tg) of PA6 increased with small VBIM loadings followed by the decreasing in Tg with further increasing the amount of VBIM. The crystallization temperature decreased with the addition of VBIM because of the strong interactions between VBIM and the PA6 matrix, as well as the dilution effect when large amounts of VBIM was introduced to the matrix. According to rheological testing, small amounts of VBIM enhanced the storage modulus and melt viscosity of PA6. Tensile tests also show an increase in strength and modulus at relatively low loadings of VBIM. The strength of PA6 with only 1 wt % VBIM improved by 108% compared to that of neat PA6. Fourier transform infrared (FTIR) investigations revealed that the ions of VBIM preferred to form hydrogen bonds with amide groups in PA6. Therefore, VBIM acts as physical connection point for the neighboring PA6 molecular chains. The specific interactions between VBIM and PA6 account not only for the enhanced melt viscosity of PA6, but also for the improved mechanical properties. Moreover, outstanding antistatic property was also observed. The surface resistivity of the sample with 1 wt % VBIM was 1.50 × 1010 Ω/sq, which means good electric dissipation property. Full article
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Open AccessArticle Electrospun Antimicrobial Polylactic Acid/Tea Polyphenol Nanofibers for Food-Packaging Applications
Polymers 2018, 10(5), 561; https://doi.org/10.3390/polym10050561
Received: 14 April 2018 / Revised: 10 May 2018 / Accepted: 16 May 2018 / Published: 22 May 2018
Cited by 1 | Viewed by 897 | PDF Full-text (2716 KB) | HTML Full-text | XML Full-text
Abstract
The development of new bioactive food-packaging materials that extend the shelf life of food is an important objective. Herein, we report the fabrication of four polylactic acid/tea polyphenol (PLA/TP) composite nanofibers, with PLA/TP ratios of 5:1, 4:1, 3:1, and 2:1, by electrospinning. The
[...] Read more.
The development of new bioactive food-packaging materials that extend the shelf life of food is an important objective. Herein, we report the fabrication of four polylactic acid/tea polyphenol (PLA/TP) composite nanofibers, with PLA/TP ratios of 5:1, 4:1, 3:1, and 2:1, by electrospinning. The morphological quality of each sample was examined by scanning electron microscopy (SEM), and samples with higher TP content were found to be deeper in color. The samples were then examined by Fourier transform infrared (FTIR) spectroscopy to confirm the presence of TP. Examination of the mechanical properties of these fibers revealed that the presence of TP decreased both tensile strength and elongation at break; however, this decrease was only slight for the PLA/TP-3:1 composite fiber. The addition of TP influenced the hydrophilic–hydrophobic property and release behavior of the composite fibers, which significantly improved the antioxidant behavior of these samples, with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacities of up to 95.07% ± 10.55% observed. Finally, antimicrobial activities against Escherichia coli and Staphylococcus aureus of up to 92.26% ± 5.93% and 94.58% ± 6.53%, respectively, were observed for the PLA/TP-3:1 composite fiber. The present study demonstrated that PLA/TP composite nanofibers can potentially be used for food-packaging applications that extend food shelf life. Full article
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Open AccessArticle Hyaluronan-Chondroitin Sulfate Anomalous Crosslinking Due to Temperature Changes
Polymers 2018, 10(5), 560; https://doi.org/10.3390/polym10050560
Received: 27 April 2018 / Revised: 17 May 2018 / Accepted: 19 May 2018 / Published: 22 May 2018
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Abstract
Glycosaminoglycans are a wide class of biopolymers showing great lubricating properties due to their structure and high affinity to water. Two of them, hyaluronic acid and chondroitin sulfate, play an important role in articular cartilage lubrication. In this work, we present results of
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Glycosaminoglycans are a wide class of biopolymers showing great lubricating properties due to their structure and high affinity to water. Two of them, hyaluronic acid and chondroitin sulfate, play an important role in articular cartilage lubrication. In this work, we present results of the all-atom molecular dynamics simulations of both molecules placed in water-based solution. To mimic changes of the physiological conditions, especially temperature, of the synovial fluid in joints under successive load (e.g., walking, jogging, jumping), simulations have been performed at different physiological temperatures in the range of 300 to 320 Kelvin (normal intra-articular temperature is 305 K). The stability of the biopolymeric network at equilibrium (isothermal and isobaric) conditions has been studied. To understand the process of physical crosslinking, the dynamics of intra- and intermolecular hydrogen bonds forming and breaking have been studied. The results show that following addition of chondroitin sulfate, hyaluronan creates more intermolecular hydrogen bonds than when in homogeneous solution. The presence of chondroitin in a hyaluronan network is beneficial as it may increase its stability. Presented data show hyaluronic acid and chondroitin sulfate as viscosity modifiers related to their crosslinking properties in different physicochemical conditions. Full article
(This article belongs to the Special Issue Mechanics of Emerging Polymers with Unprecedented Networks)
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Open AccessCommunication Polycondensation of a Perylene Bisimide Derivative and L-Malic Acid as Water-Soluble Conjugates for Fluorescent Labeling of Live Mammalian Cells
Polymers 2018, 10(5), 559; https://doi.org/10.3390/polym10050559
Received: 23 April 2018 / Revised: 16 May 2018 / Accepted: 22 May 2018 / Published: 22 May 2018
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Abstract
Based on simple mixing and polymerization of a hydroxyl-containing derivative of perylene bisimide (PBI) and l-malic acid, here, we demonstrate a new type of dye-polymer conjugate, PBI-poly(α,β-malic acid) (PBI–PMA). Benefiting from the excellent water-solubility of weak polyanionic PMA structure and the high
[...] Read more.
Based on simple mixing and polymerization of a hydroxyl-containing derivative of perylene bisimide (PBI) and l-malic acid, here, we demonstrate a new type of dye-polymer conjugate, PBI-poly(α,β-malic acid) (PBI–PMA). Benefiting from the excellent water-solubility of weak polyanionic PMA structure and the high fluorescence of PBI, the PBI-PMA conjugates readily dissolve in water, displaying strong pH-dependent fluorescence with the highest intensity at pH 6. Due to the excellent biocompatibility of PMA, those conjugates showed low cytotoxicity on L929 cells. Using L929 and HeLa cells, we also confirmed that the PBI-PMA-labeled cells display intense fluorescence. Overall, the PBI-PMA conjugate demonstrates high potential as a cell labeling agent with its synthesis ease, good solubility in aqueous medium, low cytotoxicity, and high fluorescence. Full article
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Open AccessArticle Effects of Die Configuration on the Electrical Conductivity of Polypropylene Reinforced Milled Carbon Fibers: An Application on a Bipolar Plate
Polymers 2018, 10(5), 558; https://doi.org/10.3390/polym10050558
Received: 9 April 2018 / Revised: 7 May 2018 / Accepted: 17 May 2018 / Published: 22 May 2018
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Abstract
Die configurations, filler orientations, electrical conductivity, and mechanical properties of polypropylene reinforced milled carbon fibers were studied as functions of their manufacturing processes. Series of manufacturing processes often deteriorate the material properties, hence, finding a suitable process aid is key to improving the
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Die configurations, filler orientations, electrical conductivity, and mechanical properties of polypropylene reinforced milled carbon fibers were studied as functions of their manufacturing processes. Series of manufacturing processes often deteriorate the material properties, hence, finding a suitable process aid is key to improving the electrical and mechanical properties of composite materials. Compared with the conventional manufacturing process, extrusion is a key process in the production of a highly conductive composite. A twin-screw extruder was used at a temperature of 230 °C and a rotational speed of 50 rpm before the compression molding process was carried out at 200 °C and 13 kPa. This research examined different die configurations, namely rod and sheet dies. The results indicated that the rod dies showed better mechanical properties and electrical conductivity with 25 MPa and 5 S/cm compared to the sheet dies. Moreover, rod dies are able to orientate to 86° and obtain longest filler length with 55 μm compared to the sheet dies. The alteration of the filler orientation in the produced material at a high shear rate further enhanced the electrical conductivity of the material. Full article
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Open AccessArticle Preparation, Structure, and Properties of Silk Fabric Grafted with 2-Hydroxypropyl Methacrylate Using the HRP Biocatalyzed ATRP Method
Polymers 2018, 10(5), 557; https://doi.org/10.3390/polym10050557
Received: 13 April 2018 / Revised: 18 May 2018 / Accepted: 19 May 2018 / Published: 21 May 2018
Cited by 1 | Viewed by 736 | PDF Full-text (1676 KB) | HTML Full-text | XML Full-text
Abstract
Atom transfer radical polymerization (ATRP) is a “living”/controlled radical polymerization, which is also used for surface grafting of various materials including textiles. However, the commonly used metal complex catalyst, CuBr, is mildly toxic and results in unwanted color for textiles. In order to
[...] Read more.
Atom transfer radical polymerization (ATRP) is a “living”/controlled radical polymerization, which is also used for surface grafting of various materials including textiles. However, the commonly used metal complex catalyst, CuBr, is mildly toxic and results in unwanted color for textiles. In order to replace the transition metal catalyst of surface-initiated ATRP, the possibility of HRP biocatalyst was investigated in this work. 2-hydroxypropyl methacrylate (HPMA) was grafted onto the surface of silk fabric using the horseradish peroxidase (HRP) biocatalyzed ATRP method, which is used to improve the crease resistance of silk fabric. The structure of grafted silk fabric was characterized by Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, thermogravimetic analysis, and scanning electron microscopy. The results showed that HPMA was successfully grafted onto silk fabric. Compared with the control silk sample, the wrinkle recovery property of grafted silk fabric was greatly improved, especially the wet crease recovery property. However, the whiteness, breaking strength, and moisture regain of grafted silk fabric decreased somewhat. The present work provides a novel, biocatalyzed, environmentally friendly ATRP method to obtain functional silk fabric, which is favorable for clothing application and has potential for medical materials. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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Open AccessReview Polymorphic Behavior and Phase Transition of Poly(1-Butene) and Its Copolymers
Polymers 2018, 10(5), 556; https://doi.org/10.3390/polym10050556
Received: 30 April 2018 / Revised: 17 May 2018 / Accepted: 17 May 2018 / Published: 21 May 2018
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Abstract
The properties of semicrystalline polymeric materials depend remarkably on their structures, especially for those exhibiting a polymorphic behavior. This offers an efficient way to tailor their properties through crystal engineering. For control of the crystal structure, and therefore the physical and mechanical properties,
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The properties of semicrystalline polymeric materials depend remarkably on their structures, especially for those exhibiting a polymorphic behavior. This offers an efficient way to tailor their properties through crystal engineering. For control of the crystal structure, and therefore the physical and mechanical properties, a full understanding of the polymorph selection of polymers under varied conditions is essential. This has stimulated a mass of research work on the polymorphic crystallization and related phase transformation. Considering that the isotactic poly(1-butene) (iPBu) exhibits pronounced polymorphs and complicated transition between different phases, the study on its crystallization and phase transformation has attracted considerable attention during the past decades. This review provides the context of the recent progresses made on the crystallization and phase transition behavior of iPBu. We first review the crystal structures of known crystal forms and then their formation conditions and influencing factors. In addition, the inevitable form II to form I spontaneous transition mechanism and the transformation kinetics is reviewed based on the existing research works, aiming for it to be useful for its processing in different phases and the further technical development of new methods for accelerating or even bypass its form II to form I transformation. Full article
(This article belongs to the Special Issue Phase Behavior in Polymers)
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Open AccessArticle 3D Printing of Thermoresponsive Polyisocyanide (PIC) Hydrogels as Bioink and Fugitive Material for Tissue Engineering
Polymers 2018, 10(5), 555; https://doi.org/10.3390/polym10050555
Received: 22 April 2018 / Revised: 10 May 2018 / Accepted: 15 May 2018 / Published: 21 May 2018
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Abstract
Despite the rapid and great developments in the field of 3D hydrogel printing, a major ongoing challenge is represented by the development of new processable materials that can be effectively used for bioink formulation. In this work, we present an approach to 3D
[...] Read more.
Despite the rapid and great developments in the field of 3D hydrogel printing, a major ongoing challenge is represented by the development of new processable materials that can be effectively used for bioink formulation. In this work, we present an approach to 3D deposit, a new class of fully-synthetic, biocompatible PolyIsoCyanide (PIC) hydrogels that exhibit a reverse gelation temperature close to physiological conditions (37 °C). Being fully-synthetic, PIC hydrogels are particularly attractive for tissue engineering, as their properties—such as hydrogel stiffness, polymer solubility, and gelation kinetics—can be precisely tailored according to process requirements. Here, for the first time, we demonstrate the feasibility of both 3D printing PIC hydrogels and of creating dual PIC-Gelatin MethAcrylate (GelMA) hydrogel systems. Furthermore, we propose the use of PIC as fugitive hydrogel to template structures within GelMA hydrogels. The presented approach represents a robust and valid alternative to other commercial thermosensitive systems—such as those based on Pluronic F127—for the fabrication of 3D hydrogels through additive manufacturing technologies to be used as advanced platforms in tissue engineering. Full article
(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)
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Open AccessArticle Effect of Mold Opening Process on Microporous Structure and Properties of Microcellular Polylactide–Polylactide Nanocomposites
Polymers 2018, 10(5), 554; https://doi.org/10.3390/polym10050554
Received: 18 April 2018 / Revised: 6 May 2018 / Accepted: 9 May 2018 / Published: 21 May 2018
Cited by 1 | Viewed by 706 | PDF Full-text (1362 KB) | HTML Full-text | XML Full-text
Abstract
Cell structure is a key factor that determines the final properties of microcellular polylactide (PLA) product. In the mold opening process, adjusting the rate of mold opening can effectively control cell structure. PLA and PLA composites with a void fraction as high as
[...] Read more.
Cell structure is a key factor that determines the final properties of microcellular polylactide (PLA) product. In the mold opening process, adjusting the rate of mold opening can effectively control cell structure. PLA and PLA composites with a void fraction as high as 50% were fabricated using the mold opening technique. The effects of mold opening rate and the addition of nanoclay on the cell structure, mechanical properties, and surface quality of microcellular PLA and PLA composites samples were investigated. The results showed that finer cell structure was received in the microcellular PLA samples and the surface quality was improved effectively when decreasing the rate of mold opening. The effect of mold opening rate on the foaming behavior of microcellular PLA–nanoclay was the same as that of microcellular PLA. The addition of 5 wt % nanoclay significantly improved the foaming properties, such as cell density, cell size, and structural uniformity, which consequently enhanced the mechanical properties of foams and the surface quality. Full article
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Open AccessArticle PANI Branches onto Donor-Acceptor Copolymers: Synthesis, Characterization and Electroluminescent Properties of New 2D-Materials
Polymers 2018, 10(5), 553; https://doi.org/10.3390/polym10050553
Received: 2 May 2018 / Revised: 17 May 2018 / Accepted: 17 May 2018 / Published: 21 May 2018
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Abstract
A new series of two-dimensional statistical conjugated polymers based on aniline and 9,9-dihexylfluorene as donor units and benzo- or naphtho-quinoxaline/thiadiazole derivatives as acceptor moieties, possessing PANI segments as side chains, were designed and synthesized. To investigate the effects of the perpendicular PANI branches
[...] Read more.
A new series of two-dimensional statistical conjugated polymers based on aniline and 9,9-dihexylfluorene as donor units and benzo- or naphtho-quinoxaline/thiadiazole derivatives as acceptor moieties, possessing PANI segments as side chains, were designed and synthesized. To investigate the effects of the perpendicular PANI branches on the properties of the main chain, the optical, electrochemical, morphological and electroluminescence properties were studied. The 2D materials tend to possess lower molecular weights and to absorb and to emit light red-shifted compared to the trunk 1D-polymers, in the yellow-red region of the visible spectrum. The 1D- and 2D-conjugated polymers present optical band gaps ranging from 2.15–2.55 eV, HOMO energy levels between −5.37 and −5.60 eV and LUMO energy levels between −3.02 and −3.29 eV. OLED devices based on these copolymers were fabricated. Although the performances were far from optimal due to the high turn-on voltages for which electroluminescence phenomena occur, a maximum luminescence of 55,100 cd/m2 together with a current density of 65 mA/cm2 at 18.5 V were recorded for a 2D-copolymer, PAFC6TBQ-PANI. Full article
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Open AccessArticle Enhanced Poly(Propylene Carbonate) with Thermoplastic Networks: A One-Pot Synthesis from Carbon Dioxide, Propylene Oxide, and a Carboxylic Dianhydride
Polymers 2018, 10(5), 552; https://doi.org/10.3390/polym10050552
Received: 23 April 2018 / Revised: 15 May 2018 / Accepted: 17 May 2018 / Published: 21 May 2018
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Abstract
Thermally and mechanically enhanced poly(propylene carbonate) (PPC) with networks was prepared by adding a cyclic carboxylic dianhydride, bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTCDA), in the CO2/propylene oxide (PO) copolymerization. The obtained copolymers were characterized by FT-IR, 1H NMR, DSC, and TGA. The gel,
[...] Read more.
Thermally and mechanically enhanced poly(propylene carbonate) (PPC) with networks was prepared by adding a cyclic carboxylic dianhydride, bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTCDA), in the CO2/propylene oxide (PO) copolymerization. The obtained copolymers were characterized by FT-IR, 1H NMR, DSC, and TGA. The gel, melt flow rate, hot-set elongation, and tensile properties were also measured. The formation of networks was confirmed by the presence of gel and the shape recovery after the hot-set elongation test. The minimum permanent deformation of the copolymer is 3.8% and that of PPC is 4539% higher than this value. The results show that BTCDA units are inserted into the backbone of PPC, and the PPC chains are connected successfully owing to cyclic multifunctional anhydride groups in BTCDA. With increasing feed molar ratio of BTCDA to PO from 1 to 4%, the yield strength of copolymers increases from 18.1 to 37.4 MPa compared to 12.9 MPa of PPC. The 5% weight-loss degradation temperatures and maximum weight-loss degradation temperatures greatly increase up to 276.4 and 294.7 °C, respectively, which are 58.6 °C and 55.1 °C higher than those of PPC. These enhanced properties originate from the formation of crosslinks by the rigid and bulky multifunctional dianhydride. Full article
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Open AccessReview Chemical Design of Functional Polymer Structures for Biosensors: From Nanoscale to Macroscale
Polymers 2018, 10(5), 551; https://doi.org/10.3390/polym10050551
Received: 20 April 2018 / Revised: 14 May 2018 / Accepted: 14 May 2018 / Published: 21 May 2018
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Abstract
Over the past decades, biosensors, a class of physicochemical detectors sensitive to biological analytes, have drawn increasing interest, particularly in light of growing concerns about human health. Functional polymeric materials have been widely researched for sensing applications because of their structural versatility and
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Over the past decades, biosensors, a class of physicochemical detectors sensitive to biological analytes, have drawn increasing interest, particularly in light of growing concerns about human health. Functional polymeric materials have been widely researched for sensing applications because of their structural versatility and significant progress that has been made concerning their chemistry, as well as in the field of nanotechnology. Polymeric nanoparticles are conventionally used in sensing applications due to large surface area, which allows rapid and sensitive detection. On the macroscale, hydrogels are crucial materials for biosensing applications, being used in many wearable or implantable devices as a biocompatible platform. The performance of both hydrogels and nanoparticles, including sensitivity, response time, or reversibility, can be significantly altered and optimized by changing their chemical structures; this has encouraged us to overview and classify chemical design strategies. Here, we have organized this review into two main sections concerning the use of nanoparticles and hydrogels (as polymeric structures) for biosensors and described chemical approaches in relevant subcategories, which act as a guide for general synthetic strategies. Full article
(This article belongs to the Special Issue Polymer Based Bio-Sensors)
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Open AccessArticle The Preparation of Nano-SiO2/Dialdehyde Cellulose Hybrid Materials as a Novel Cross-Linking Agent for Collagen Solutions
Polymers 2018, 10(5), 550; https://doi.org/10.3390/polym10050550
Received: 29 March 2018 / Revised: 9 May 2018 / Accepted: 15 May 2018 / Published: 21 May 2018
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Abstract
Nano-SiO2 was immobilized onto dialdehyde cellulose (DAC) to prepare SiO2/DAC hybrid materials. Fourier transform infrared spectra (FTIR), thermogravimetric analysis and field emission scanning electron microscopy of SiO2/DAC indicated that nano-SiO2 had been successfully hybridized with DAC. X-ray
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Nano-SiO2 was immobilized onto dialdehyde cellulose (DAC) to prepare SiO2/DAC hybrid materials. Fourier transform infrared spectra (FTIR), thermogravimetric analysis and field emission scanning electron microscopy of SiO2/DAC indicated that nano-SiO2 had been successfully hybridized with DAC. X-ray diffraction suggested that the structure of DAC was influenced by the nano-SiO2. SiO2/DAC was then used as the cross-linker of collagen solutions. Gel electrophoresis patterns and FTIR reflected that cross-linking occurred between DAC and collagen, but that collagen retained the native triple-helix, respectively. Differential scanning calorimetry indicated that the thermal stability of collagen could be effectively improved by SiO2/DAC. Dynamic rheology tests revealed that the flowability of collagens cross-linked by SiO2/DAC was superior to that of those cross-linked by DAC; meanwhile, collagens cross-linked by SiO2/DAC possessed a more homogeneous morphology compared to those cross-linked by DAC. The hybridization of SiO2/DAC as a cross-linker for collagen could effectively prevent the gelation caused by excessive cross-linking, and significantly improve the thermostability of collagen, which could be helpful for collagen being applied in fields including biomaterials, cosmetics, etc. Full article
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Open AccessArticle The Effects of Hybridization on the Flexural Performances of Carbon/Glass Interlayer and Intralayer Composites
Polymers 2018, 10(5), 549; https://doi.org/10.3390/polym10050549
Received: 23 March 2018 / Revised: 9 May 2018 / Accepted: 17 May 2018 / Published: 20 May 2018
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Abstract
The effects of hybridization on the flexural properties of interlayer and intralayer Carbon/Glass (C/G) composites were explored in this work. First, the theoretical analysis of stress distribution on interlayer hybrid composites was discussed. The experimental results showed that the layer structure is the
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The effects of hybridization on the flexural properties of interlayer and intralayer Carbon/Glass (C/G) composites were explored in this work. First, the theoretical analysis of stress distribution on interlayer hybrid composites was discussed. The experimental results showed that the layer structure is the critical factor affecting the flexural properties for interlayer hybrid composites, and the mixed ratio has no obvious impact. Since the carbon fiber is distributed at the top or bottom surface, the interlayer composites can obtain the maximum flexural modulus. Some structures can even achieve the same modulus as the pure carbon composites, and an excellent flexural strength can be attained with the carbon fiber located in the bottom layer. In terms of the intralayer hybrid composites, the fracture strain, flexural modulus, and flexural strength basically change linearly as the glass fiber content increases, which is consistent with the calculated values via the rule of mixture (ROM). Additionally, the C/G mixed ratio has a decisive effect on the flexural properties of intralayer hybrid composites; however, they are affected weakly by the layer structure. In general, some structures of the interlayer hybrid composites exhibit better flexural properties than that of the intralayer hybrid composites at the same C/G hybrid ratio; the alterations in layer structures make it possible to obtain excellent flexural properties for interlayer hybrid composites with less carbon fiber. Full article
(This article belongs to the Special Issue Textile and Textile-Based Materials)
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Open AccessArticle Molecular Weight-Dependent Activity of Aminated Poly(α)glutamates as siRNA Nanocarriers
Polymers 2018, 10(5), 548; https://doi.org/10.3390/polym10050548
Received: 25 April 2018 / Revised: 14 May 2018 / Accepted: 15 May 2018 / Published: 20 May 2018
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Abstract
RNA interference (RNAi) can contribute immensely to the area of personalized medicine by its ability to target any gene of interest. Nevertheless, its clinical use is limited by lack of efficient delivery systems. Polymer therapeutics can address many of the challenges encountered by
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RNA interference (RNAi) can contribute immensely to the area of personalized medicine by its ability to target any gene of interest. Nevertheless, its clinical use is limited by lack of efficient delivery systems. Polymer therapeutics can address many of the challenges encountered by the systemic delivery of RNAi, but suffer from inherent drawbacks such as polydispersity and batch to batch heterogeneity. These characteristics may have far-reaching consequences when dealing with therapeutic applications, as both the activity and the toxicity may be dependent on the length of the polymer chain. To investigate the consequences of polymers’ heterogeneity, we have synthesized two batches of aminated poly(α)glutamate polymers (PGAamine), differing in their degree of polymerization, but not in the monomer units or their conjugation. Isothermal titration calorimetry study was conducted to define the binding affinity of these polymers with siRNA. Molecular dynamics simulation revealed that Short PGAamine:siRNA polyplexes exposed a higher amount of amine moieties to the surroundings compared to Long PGAamine. This resulted in a higher zeta potential, leading to faster degradation and diminished gene silencing. Altogether, our study highlights the importance of an adequate physico-chemical characterization to elucidate the structure–function-activity relationship, for further development of tailor-designed RNAi delivery vehicles. Full article
(This article belongs to the Special Issue Polymers for Therapy and Diagnostics)
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Open AccessArticle Properties and Fabrication of PA66/Surface-Modified Multi-Walled Nanotubes Composite Fibers by Ball Milling and Melt-Spinning
Polymers 2018, 10(5), 547; https://doi.org/10.3390/polym10050547
Received: 11 April 2018 / Revised: 9 May 2018 / Accepted: 15 May 2018 / Published: 19 May 2018
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Abstract
PA66/surface-modified multi-walled carbon nanotubes (MWNTs) composite fibers with a better dispersion and a stronger interfacial interaction between MWNTs and polyamide 66 (PA66) matrix were fabricated via the method of ball milling and melt-spinning. The effects of unmodified (U-MWNTs), acid-modified (MWNTs-COOH) and sodium dodecyl
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PA66/surface-modified multi-walled carbon nanotubes (MWNTs) composite fibers with a better dispersion and a stronger interfacial interaction between MWNTs and polyamide 66 (PA66) matrix were fabricated via the method of ball milling and melt-spinning. The effects of unmodified (U-MWNTs), acid-modified (MWNTs-COOH) and sodium dodecyl benzenesulfonate-modified MWNTs (MWNTs-SDBS) on the physical mechanical and thermal properties of PA66 were investigated. The results show that, the surface modified nanotube can provide homogeneous dispersion and there is a strong interfacial bonding between PA66 and MWNTs-COOH. A homogeneous dispersion of MWNTs in PA66 matrices without agglomeration is obtained by a facile ball milling method, which can increase the utilization ratio of MWNTs, reduce the required amount of MWNTs and ultimately improve the mechanical properties at a lower filler loading. The tensile strength of composite fibers reaches a maximum which respectively improved by 27% and 24% than that of PA66 fibers, when the mass fraction of MWNTs-SDBS and MWNTs-COOH is 0.1%. It is helpful for decrease the producing costa of the composite fibers. Moreover, the incorporation of MWNTs into PA66 improves the crystallizing temperature, crystallinity and thermal stability. The research shows that a novel facile method is developed for the fabrication of polymer composite fiber. Full article
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Open AccessArticle High Performance Soluble Polyimides from Ladder-Type Fluorinated Dianhydride with Polymorphism
Polymers 2018, 10(5), 546; https://doi.org/10.3390/polym10050546
Received: 20 April 2018 / Revised: 15 May 2018 / Accepted: 16 May 2018 / Published: 18 May 2018
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Abstract
A novel rigid semi-alicyclic dianhydride 9,10-difluoro-9,10-bis(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetracarboxylic acid dianhydride (8FDA) was reported, and its single crystal X-ray diffraction result revealed the existence of the polymorphic structure in this compound. The detail geometric configuration transition during the synthesized process was investigated, exhibiting a transition of
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A novel rigid semi-alicyclic dianhydride 9,10-difluoro-9,10-bis(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetracarboxylic acid dianhydride (8FDA) was reported, and its single crystal X-ray diffraction result revealed the existence of the polymorphic structure in this compound. The detail geometric configuration transition during the synthesized process was investigated, exhibiting a transition of from trans- to cis- when the hydroxyl groups were substituted by fluoride with diethylaminosulfur trifluoride (DAST). Compared with the dianhydride 4,4′-(Hexaflouroisopropylidene) diphthalic anhydride (6FDA) and 1S,2R,4S,5R-cyclohexanetetracarboxylic dianhydride (HPMDA), the resulting polyimide (PI) films based on 8FDA exhibited an obviously higher glass transition temperature (Tg, 401 °C) and a much lower coefficient of thermal expansion (CTE, 14 ppm K−1). This indicates that 8FDA is an ideal building block in high-performance soluble PIs with low CTE. Full article
(This article belongs to the Special Issue Aromatic Polymers)
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Open AccessArticle Lamellae Assembly in Dendritic Spherulites of Poly(l-lactic Acid) Crystallized with Poly(p-Vinyl Phenol)
Polymers 2018, 10(5), 545; https://doi.org/10.3390/polym10050545
Received: 19 April 2018 / Revised: 8 May 2018 / Accepted: 14 May 2018 / Published: 18 May 2018
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Abstract
Lamellar assembly with fractal-patterned growth into dendritic and ringed spherulites of crystallized poly(l-lactic acid) (PLLA), of two molecular weight (MW) grades and crystallized at (temperature of crystallization) Tc = 120 and 130 °C, respectively, are evaluated using optical and atomic-force
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Lamellar assembly with fractal-patterned growth into dendritic and ringed spherulites of crystallized poly(l-lactic acid) (PLLA), of two molecular weight (MW) grades and crystallized at (temperature of crystallization) Tc = 120 and 130 °C, respectively, are evaluated using optical and atomic-force microscopies. The results of surface-relief patterns in correlation with interior microscopy analyses in this work strongly indicate that the observed birefringence changes in PLLA polymer dendritic or ringed spherulites (from blue to orange, or to optical extinction) need not be definitely associated with the continuous helix twisting of lamellae; they can be caused by sudden and discontinuous lamellae branching at intersected angles with respect to the original main lamellae, as proven in the case of dendritic and zig-zag rough-ringed spherulites. Intersection angles between the main stalks and branches tend to be governed by polymer crystal lattices; for PLLA, the orthorhombic lattice (α-form) usually gives a 60° angle of branching and hexagonal growth. The branching lamellae then further bend to convex or concave shapes and finally make a 60–90° angle with respect to the main stalks. Such mechanisms are proven to exist in the straight dendritic/striped high-molecular weight (HMW)-PLLA spherulites (Tc = 120 °C); similar mechanisms also work in circularly ringed (Tc = 130 °C) HMW-PLLA spherulites. Full article
(This article belongs to the Special Issue Phase Behavior in Polymers)
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Open AccessArticle Hybrid Materials Based on Poly-3-amine-7-methylamine-2-methylphenazine and Magnetite Nanoparticles Immobilized on Single-Walled Carbon Nanotubes
Polymers 2018, 10(5), 544; https://doi.org/10.3390/polym10050544
Received: 28 April 2018 / Revised: 14 May 2018 / Accepted: 15 May 2018 / Published: 18 May 2018
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Abstract
Polymer-metal-carbon hybrid nanomaterials based on thermostable electroactive poly-3-amine-7-methylamine-2-methylphenazine (PAMMP), single walled carbon nanotubes (SWCNT), and magnetite (Fe3O4) nanoparticles were synthesized for the first time. Hybrid Fe3O4/SWCNT/PAMMP nanomaterial synthesis was carried out via in situ chemical
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Polymer-metal-carbon hybrid nanomaterials based on thermostable electroactive poly-3-amine-7-methylamine-2-methylphenazine (PAMMP), single walled carbon nanotubes (SWCNT), and magnetite (Fe3O4) nanoparticles were synthesized for the first time. Hybrid Fe3O4/SWCNT/PAMMP nanomaterial synthesis was carried out via in situ chemical oxidative polymerization of 3-amine-7-methylamine-2-methylphenazine hydrochloride in the presence of metal-carbon Fe3O4/SWCNT nanocomposites. Fe3O4/SWCNT nanocomposites were obtained by the immobilization of magnetite nanoparticles on the SWCNT surface in the course of Fe3O4 nanoparticles synthesis in alkaline medium. The developed nanocomposite materials were characterized by FTIR spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission (FE-SEM) scanning electron microscopy, atomic absorption spectrometry (AAS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and magnetometry. The chemical structure and phase composition, magnetic and electrical properties, and thermal stability of the obtained multifunctional nanomaterials, depending on synthesis conditions, were investigated. Full article
(This article belongs to the Special Issue Polymer Hybrid Materials)
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Open AccessArticle Isothermal and Nonisothermal Crystallization Kinetics of Poly(ε-caprolactone) Blended with a Novel Ionic Liquid, 1-Ethyl-3-propylimidazolium Bis(trifluoromethanesulfonyl)imide
Polymers 2018, 10(5), 543; https://doi.org/10.3390/polym10050543
Received: 29 March 2018 / Revised: 28 April 2018 / Accepted: 16 May 2018 / Published: 18 May 2018
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Abstract
Recently, ionic liquids (ILs) and biodegradable polymers have become crucial functional materials in green sustainable science and technology. In this study, we investigated the influence of a novel IL, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide ([EPrI][TFSI]), on the crystallization kinetics of a widely studied biodegradable polymer, poly(ε-caprolactone)
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Recently, ionic liquids (ILs) and biodegradable polymers have become crucial functional materials in green sustainable science and technology. In this study, we investigated the influence of a novel IL, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide ([EPrI][TFSI]), on the crystallization kinetics of a widely studied biodegradable polymer, poly(ε-caprolactone) (PCL). To obtain a comprehensive understanding, both the isothermal and nonisothermal crystallization kinetics of the PCL blends were studied. Incorporating [EPrI][TFSI] reduced the isothermal and nonisothermal crystallization rates of PCL. Regarding isothermal crystallization, the small k and 1/t0.5 values of the blend, estimated using the Avrami equation, indicated that [EPrI][TFSI] decreased the rate of isothermal crystallization of PCL. The Mo model adequately described the nonisothermal crystallization kinetics of the blends. Increasing the [EPrI][TFSI] content caused the rate-related parameter F(T) to increase. This indicated that the crystallization rate of PCL decreased when [EPrI][TFSI] was incorporated. The spherulite appearance temperature of the blending sample was found to be lower than that of neat PCL under a constant cooling rate. The analysis of the effective activation energy proposed that the nonisothermal crystallization of PCL would not be favorited when the [EPrI][TFSI] was incorporated into the blends. The addition of [EPrI][TFSI] would not change the crystal structures of PCL according to the results of wide angle X-ray diffraction. Fourier transform infrared spectroscopy suggested that interactions occurred between [EPrI][TFSI] and PCL. The crystallization kinetics of PCL were inhibited when [EPrI][TFSI] was incorporated. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessReview Multifunctional Polymer Nanocomposites Reinforced by Aligned Carbon Nanomaterials
Polymers 2018, 10(5), 542; https://doi.org/10.3390/polym10050542
Received: 20 April 2018 / Revised: 14 May 2018 / Accepted: 16 May 2018 / Published: 17 May 2018
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Abstract
Carbon nanomaterials such as carbon black (CB), carbon nanotubes (CNTs), and graphene have demonstrated significant potential as fillers to improve the electrical, thermal, and mechanical properties of polymers and their fiber-reinforced polymer composites. The level of improvement has been found to depend significantly
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Carbon nanomaterials such as carbon black (CB), carbon nanotubes (CNTs), and graphene have demonstrated significant potential as fillers to improve the electrical, thermal, and mechanical properties of polymers and their fiber-reinforced polymer composites. The level of improvement has been found to depend significantly on the degree of alignment of carbon nanomaterials. Due to the very small scale and complex interactions of carbon nanomaterials with polymers and structural fibers, alignment in a given direction has been a major challenge. Over the past decade, considerable effort has been devoted to developing effective strategies to align carbon nanomaterials in polymer matrices. However, significant technological challenges remain, and there is still a lack of understanding of the alignment mechanisms and their effects on the properties of polymers and composites. This paper reviews in situ alignment techniques including shear deformation, mechanical stretching, electrospinning, and application of an external magnetic or electric field, and ex situ techniques including using vertically grown CNTs or graphene. This review particularly focuses on physical mechanisms underpinning the magnetic or electric field-induced alignment and theoretical analyses that describe the different motions occurring and the major parameters controlling alignment. Moreover, this review highlights the recent research findings of the effects of alignment on the properties of polymer nanocomposites. The outlook towards the challenges and opportunities in this field are also discussed in this review. Full article
(This article belongs to the Special Issue Polymer Hybrids and Composites)
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Open AccessArticle Oral Delivery of Curcumin Polymeric Nanoparticles Ameliorates CCl4-Induced Subacute Hepatotoxicity in Wistar Rats
Polymers 2018, 10(5), 541; https://doi.org/10.3390/polym10050541
Received: 22 March 2018 / Revised: 28 April 2018 / Accepted: 11 May 2018 / Published: 17 May 2018
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Abstract
Curcumin is the major bioactive compound of Curcuma longa, an important medicinal plant used in traditional herbal formulations since ancient times. In the present study, we report that curcumin nanoparticles (ηCur) protects Wistar rats against carbon tetrachloride (CCl4)-induced subacute hepatotoxicity.
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Curcumin is the major bioactive compound of Curcuma longa, an important medicinal plant used in traditional herbal formulations since ancient times. In the present study, we report that curcumin nanoparticles (ηCur) protects Wistar rats against carbon tetrachloride (CCl4)-induced subacute hepatotoxicity. Nanoparticles of sizes less than 220 nm with spherical shape were prepared using PLGA and PVA respectively as polymer and stabilizer. Test animals were injected via intraperitoneal route with 1 mL/kg CCl4 (8% in olive oil) twice a week over a period of 8 weeks to induce hepatotoxicity. On the days following the CCl4 injection, test animals were orally administered with either curcumin or its equivalent dose of ηCur. Behavioural observation, biochemical analysis of serum and histopathological examination of liver of the experimental animals indicated that ηCur offer significantly higher hepatoprotection compared to curcumin. Full article
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Open AccessCommunication Intrinsic Fluorescence of PAMAM Dendrimers—Quenching Studies
Polymers 2018, 10(5), 540; https://doi.org/10.3390/polym10050540
Received: 5 April 2018 / Revised: 10 May 2018 / Accepted: 15 May 2018 / Published: 17 May 2018
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Abstract
Intrinsic, non-traditional fluorescence of polyamidoamine (PAMAM) dendrimers that do not possess classical fluorophores has been attracting considerable interest for the last decade. Many hypotheses regarding the source of the fluorescence have appeared, but some of them are still disputable. In order to shed
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Intrinsic, non-traditional fluorescence of polyamidoamine (PAMAM) dendrimers that do not possess classical fluorophores has been attracting considerable interest for the last decade. Many hypotheses regarding the source of the fluorescence have appeared, but some of them are still disputable. In order to shed new light on the nature of the phenomenon, we applied quenchers that are normally used to study intrinsic fluorescence of proteins (i.e., KI, CsCl, and acrylamide). KI and acrylamide efficiently quenched steady state fluorescence of PAMAM G2, PAMAM G3, and PAMAM G4 dendrimers. Stern-Volmer plots exhibited a downward curvature that has been elucidated by heterogenous emission. We assume that there are two distinct fluorescent moieties in the dendrimer structure that are characterized by different accessibility to the quenchers. Full article
(This article belongs to the Special Issue Polymer Characterization)
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Open AccessArticle Effects of Thermal Cross-Linking on the Structure and Property of Asymmetric Membrane Prepared from the Polyacrylonitrile
Polymers 2018, 10(5), 539; https://doi.org/10.3390/polym10050539
Received: 23 March 2018 / Revised: 27 April 2018 / Accepted: 14 May 2018 / Published: 17 May 2018
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Abstract
Improving the thermal and chemical stabilities of classical polymer membranes will be beneficial to extend their applications in the high temperature or aggressive environment. In this work, the asymmetric ultrafiltration membranes prepared from the polyacrylonitrile (PAN) were used to fabricate the cross-linking asymmetric
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Improving the thermal and chemical stabilities of classical polymer membranes will be beneficial to extend their applications in the high temperature or aggressive environment. In this work, the asymmetric ultrafiltration membranes prepared from the polyacrylonitrile (PAN) were used to fabricate the cross-linking asymmetric (CLA) PAN membranes via thermal cross-linking in air to improve their thermal and chemical stabilities. The effects of thermal cross-linking parameters such as temperature and holding time on the structure, gas separation performance, thermal and chemical stabilities of PAN membranes were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), positron annihilation lifetime spectroscopy (PALS), scanning electron microscopy (SEM), thermogravimetic analysis (TGA) and gas permeation test. The thermal cross-linking significantly influences the chemical structure, microstructure and pore structure of PAN membrane. During the thermal cross-linking, the shrinkage of membrane and coalescence or collapse of pore and microstructure make large pores diminish, small pores disappear and pore volumes reduce. The gas permeances of CLA-PAN membranes increase as the increasing of cross-linking temperature and holding time due to the volatilization of small molecules. The CLA-PAN membranes demonstrate excellent thermal and chemical stabilities and present good prospects for application in ultrafiltration for water treatment and for use as a substrate for nanofiltration or gas separation with an aggressive and demanding environment. Full article
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Open AccessArticle Renewable Resources and a Recycled Polymer as Raw Materials: Mats from Electrospinning of Lignocellulosic Biomass and PET Solutions
Polymers 2018, 10(5), 538; https://doi.org/10.3390/polym10050538
Received: 6 April 2018 / Revised: 10 May 2018 / Accepted: 14 May 2018 / Published: 17 May 2018
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Abstract
Interest in the use of renewable raw materials in the preparation of materials has been growing uninterruptedly in recent decades. The aim of this strategy is to offer alternatives to the use of fossil fuel-based raw materials and to meet the demand for
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Interest in the use of renewable raw materials in the preparation of materials has been growing uninterruptedly in recent decades. The aim of this strategy is to offer alternatives to the use of fossil fuel-based raw materials and to meet the demand for materials that are less detrimental to the environment after disposal. In this context, several studies have been carried out on the use of lignocellulosic biomass and its main components (cellulose, hemicelluloses, and lignin) as raw materials for polymeric materials. Lignocellulosic fibers have a high content of cellulose, but there has been a notable lack of investigations on application of the electrospinning technique for solutions prepared from raw lignocellulosic biomass, even though the presence of cellulose favors the alignment of the fiber chains during electrospinning. In this investigation, ultrathin (submicrometric) and nanoscale aligned fibers were successfully prepared via electrospinning (room temperature) of solutions prepared with different contents of lignocellulosic sisal fibers combined with recycled poly(ethylene terephthalate) (PET) using trifluoroacetic acid (TFA) as solvent. The “macro” fibers were deconstructed by the action of TFA, resulting in solutions containing their constituents, i.e., cellulose, hemicelluloses, and lignin, in addition to PET. The “macro” sisal fibers were reconstructed at the nanometer and submicrometric scale from these solutions. The SEM micrographs of the mats containing the components of sisal showed distinct fiber networks, likely due to differences in the solubility of these components in TFA and in their dielectric constants. The mechanical properties of the mats (dynamic mechanical analysis, DMA, and tensile properties) were evaluated with the samples positioned both in the direction (dir) of and in opposition (op) to the alignment of the nano and ultrathin fibers, which can be considered a novelty in the analysis of this type of material. DMA showed superior values of storage modulus (E’ at 30 °C) for the mats characterized in the preferential direction of fiber alignment. For example, for mats obtained from solutions prepared from a 0.4 ratio of sisal fibers/PET, Sisal/PET0.40dir presented a high E’ value of 765 MPa compared to Sisal/PET0.40op that presented an E’ value of 88.4 MPa. The fiber alignment did not influence the Tg values (from tan δ peak) of electrospun mats with the same compositions, as they presented similar values for this property. The tensile properties of the electrospun mats were significantly impacted by the alignment of the fibers: e.g., Sisal/PET0.40dir presented a high tensile strength value of 15.72 MPa, and Sisal/PET0.40op presented a value of approximately 2.5 MPa. An opposite trend was observed regarding the values of elongation at break for these materials. Other properties of the mats are also discussed; such as the index of fiber alignment, average porosity, and surface contact angle. To our knowledge, this is the first time that the influence of fiber alignment on the properties of electrospun mats based on untreated lignocellulosic biomass combined with a recycled polymer, such as PET, has been evaluated. The mats obtained in this study have potential for diversified applications, such as reinforcement for polymeric matrices in nanocomposites, membranes for filtration, and support for enzymes, wherein the fiber alignment, together with other evaluated properties, can impact their effectiveness in these applications. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle Thermal and Mechanical Behavior of New Transparent Thermoplastic Polyurethane Elastomers Derived from Cycloaliphatic Diisocyanate
Polymers 2018, 10(5), 537; https://doi.org/10.3390/polym10050537
Received: 25 April 2018 / Revised: 11 May 2018 / Accepted: 14 May 2018 / Published: 16 May 2018
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Abstract
New transparent thermoplastic polyurethane elastomers (TPURs) with the hard-segment content of ≈50 mass % were synthesized by one-step melt polyaddition of 1,1′-methanediylbis(4-isocyanatocyclohexane), 2,2′-methylenebis[(4,1-phenylene)-methylenesulfanediyl]diethanol (diol E), 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid (DMPA), a poly(oxytetramethylene) diol of M¯n = 1000 g/mol (PTMO), or a poly(hexametylene carbonate)
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New transparent thermoplastic polyurethane elastomers (TPURs) with the hard-segment content of ≈50 mass % were synthesized by one-step melt polyaddition of 1,1′-methanediylbis(4-isocyanatocyclohexane), 2,2′-methylenebis[(4,1-phenylene)-methylenesulfanediyl]diethanol (diol E), 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid (DMPA), a poly(oxytetramethylene) diol of M ¯ n = 1000 g/mol (PTMO), or a poly(hexametylene carbonate) diol of M ¯ n = 860 g/mol (PHCD). Herein, I prepared TPURs in which 20, 40, and 60 mol % of diol E was replaced with DMPA, an ionic chain extender. The structure of polymers was examined by ATR-FTIR. Their thermal and mechanical behaviors were determined by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile tests, and Shore A/D hardness. Their optical properties are described. Generally, the addition of carboxyl groups to the polymer resulted in decreases in their thermal stability, transparency, and refractive indexes. Furthermore, the use of different soft segments revealed significant differences in both mechanical and thermal properties of the polymers obtained. Full article
(This article belongs to the Special Issue Elastomers)
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Open AccessArticle Effect of Chemical Disinfection on Chitosan Coated PMMA and PETG Surfaces—An In Vitro Study
Polymers 2018, 10(5), 536; https://doi.org/10.3390/polym10050536
Received: 27 February 2018 / Revised: 2 May 2018 / Accepted: 9 May 2018 / Published: 16 May 2018
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Abstract
In oral sciences, chitosan application is of interest due to its antimicrobial and hemostatic activity. Chitosan coating of dentures and other intraoral devices could be beneficial for treatment of denture stomatitis or in the management of postoperative bleeding. Disinfection of dentures and prosthodontic
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In oral sciences, chitosan application is of interest due to its antimicrobial and hemostatic activity. Chitosan coating of dentures and other intraoral devices could be beneficial for treatment of denture stomatitis or in the management of postoperative bleeding. Disinfection of dentures and prosthodontic materials is crucial before their use in patients. This study investigated the influence of chemical disinfectants on chitosan-coated surfaces. A total of 100 specimens were made: 50 of PMMA (polymethyl methacrylate), and 50 of PETG (polyethylene terephthalate glycol-modified) material and coated with 2% chitosan acetate solution. In each material, 5 groups (10 specimens each) were established and disinfected with Printosept-ID (L1), MD 520 (L2), Silosept (L3), or Dentavon (L4), or stored in distilled water (L0, control group). After disinfection, all specimens underwent abrasion tests (30,000 cycles in a tooth-brushing simulator). Areas without chitosan coating were measured by digital planimetry both before and after the disinfection/abrasion procedure and a damage-score was calculated. Regarding chitosan coating, the statistical analysis showed a significant influence of the disinfectants tested and significant differences between disinfectants (p < 0.05). Chitosan coating was most stable on PMMA and PETG after disinfection with MD 520 (L2). Otherwise, active oxygen containing disinfectants (L3, L4) led to the greatest alterations in the chitosan coating. Full article
(This article belongs to the Special Issue Polymerizations from Surfaces)
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Open AccessArticle High Performance Clean Fracturing Fluid Using a New Tri-Cationic Surfactant
Polymers 2018, 10(5), 535; https://doi.org/10.3390/polym10050535
Received: 20 April 2018 / Revised: 4 May 2018 / Accepted: 5 May 2018 / Published: 16 May 2018
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Abstract
In order to improve the heat resistance of current clean fracturing fluids, a novel cationic surfactant (VES-T), composed of three single-chains and a spacer group, was designed and synthesized as thickener for the fluids. Various performances of such VES-T fluid in the presence
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In order to improve the heat resistance of current clean fracturing fluids, a novel cationic surfactant (VES-T), composed of three single-chains and a spacer group, was designed and synthesized as thickener for the fluids. Various performances of such VES-T fluid in the presence of NaSal were evaluated carefully. Study of the rheological properties demonstrated that the fluids with varying concentrations (3–5 wt %) of VES-T have excellent thermal stabilities under ultra-high temperatures ranging from 140 to 180 °C. Until now, this is the highest temperature that the VES fracturing fluid could bear. The VES-T/NaSal fluid exhibited good viscoelasticity and proppant-suspending capability, which was attributed to the three-dimensional network formed by entangled wormlike micelles. Furthermore, the VES fracturing fluids can be completely gel broken by standard brines within 2 h. Thus, the VES-T synthesized in this work has a good prospect for utilization during the development of ultra-high temperature reservoirs. Full article
(This article belongs to the Special Issue Smart and Functional Elastomers, Hydrogels, and Ionogels)
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Open AccessFeature PaperArticle The Relationship between Bulk Silicone and Benzophenone-Initiated Hydrogel Coating Properties
Polymers 2018, 10(5), 534; https://doi.org/10.3390/polym10050534
Received: 21 April 2018 / Revised: 4 May 2018 / Accepted: 9 May 2018 / Published: 16 May 2018
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Abstract
Polydimethylsiloxane (PDMS) is a silicone elastomer-based material that is used in various applications, including coatings, tubing, microfluidics, and medical implants. PDMS has been modified with hydrogel coatings to prevent fouling, which can be done through UV-mediated free radical polymerization using benzophenone. However, to
[...] Read more.
Polydimethylsiloxane (PDMS) is a silicone elastomer-based material that is used in various applications, including coatings, tubing, microfluidics, and medical implants. PDMS has been modified with hydrogel coatings to prevent fouling, which can be done through UV-mediated free radical polymerization using benzophenone. However, to the best of our knowledge, the properties of hydrogel coatings and their influence on the bulk properties of PDMS under various preparation conditions, such as the type and concentration of monomers, and UV treatment time, have never been investigated. Acrylate-based monomers were used to perform free radical polymerization on PDMS surfaces under various reaction conditions. This approach provides insights into the relationship between the hydrogel coating and bulk properties of PDMS. Altering the UV polymerization time and the monomer concentration resulted in different morphologies with different roughness and thickness of the hydrogel coating, as well as differences in the bulk material stiffness. The surface morphology of the coated PDMS was characterized by AFM. The cross section and thickness of the coatings were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The dependence of coating development on the monomer type and concentration used was evaluated by surface hydrophilicity, as measured by water contact angle. Elongation-until-break analysis revealed that specific reaction conditions affected the bulk properties and made the coated PDMS brittle. Therefore, boundary conditions have been identified to enable high quality hydrogel coating formation without affecting the bulk properties of the material. Full article
(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)
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