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Polymers, Volume 12, Issue 10 (October 2020) – 262 articles

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Cover Story (view full-size image) Engineering applications of hydrogels are generally limited by the common problem of their softness [...] Read more.
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Open AccessReview
Directed Self-Assembly of Block Copolymers for the Fabrication of Functional Devices
Polymers 2020, 12(10), 2432; https://doi.org/10.3390/polym12102432 - 21 Oct 2020
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Abstract
Directed self-assembly of block copolymers is a bottom-up approach to nanofabrication that has attracted high interest in recent years due to its inherent simplicity, high throughput, low cost and potential for sub-10 nm resolution. In this paper, we review the main principles of [...] Read more.
Directed self-assembly of block copolymers is a bottom-up approach to nanofabrication that has attracted high interest in recent years due to its inherent simplicity, high throughput, low cost and potential for sub-10 nm resolution. In this paper, we review the main principles of directed self-assembly of block copolymers and give a brief overview of some of the most extended applications. We present a novel fabrication route based on the introduction of directed self-assembly of block copolymers as a patterning option for the fabrication of nanoelectromechanical systems. As a proof of concept, we demonstrate the fabrication of suspended silicon membranes clamped by dense arrays of single-crystal silicon nanowires of sub-10 nm diameter. Resulting devices can be further developed for building up high-sensitive mass sensors based on nanomechanical resonators. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Spain (2020,2021))
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Open AccessArticle
Radiation Processing and Characterization of Some Ethylene-propylene-diene Terpolymer/Butyl (Halobutyl) Rubber/Nanosilica Composites
Polymers 2020, 12(10), 2431; https://doi.org/10.3390/polym12102431 - 21 Oct 2020
Viewed by 210
Abstract
Composites based on ethylene–propylene–diene terpolymer (EPDM), butyl/halobutyl rubber and nanosilica were prepared by melt mixing and subjected to different doses of electron beam irradiation. The effect of irradiation dose on the mechanical properties, morphology, glass transition temperature, thermal stability and water uptake [...] Read more.
Composites based on ethylene–propylene–diene terpolymer (EPDM), butyl/halobutyl rubber and nanosilica were prepared by melt mixing and subjected to different doses of electron beam irradiation. The effect of irradiation dose on the mechanical properties, morphology, glass transition temperature, thermal stability and water uptake was investigated. The efficiency of the crosslinking by electron beam irradiation was analyzed by Charlesby–Pinner parameter evaluation and crosslink density measurements. The scanning electron microscopy data showed a good dispersion of nanosilica in the rubber matrix. An improvement in hardness and 100% modulus was revealed by increasing irradiation dose up to 150 kGy. The interaction between polymer matrix and nanosilica was analyzed using the Kraus equation. Additionally, these results indicated that the mechanical properties, surface characteristics, and water uptake were dependent on crosslink characteristics. Full article
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Open AccessArticle
PVDF-BaTiO3 Nanocomposite Inkjet Inks with Enhanced β-Phase Crystallinity for Printed Electronics
Polymers 2020, 12(10), 2430; https://doi.org/10.3390/polym12102430 - 21 Oct 2020
Viewed by 181
Abstract
Polyvinylidene difluoride (PVDF) and its copolymers are promising electroactive polymers showing outstanding ferroelectric, piezoelectric, and pyroelectric properties in comparison with other organic materials. They have shown promise for applications in flexible sensors, energy-harvesting transducers, electronic skins, and flexible memories due to their biocompatibility, [...] Read more.
Polyvinylidene difluoride (PVDF) and its copolymers are promising electroactive polymers showing outstanding ferroelectric, piezoelectric, and pyroelectric properties in comparison with other organic materials. They have shown promise for applications in flexible sensors, energy-harvesting transducers, electronic skins, and flexible memories due to their biocompatibility, high chemical stability, bending and stretching abilities. PVDF can crystallize at five different phases of α, β, γ, δ, and ε; however, ferro-, piezo-, and pyroelectric properties of this polymer only originate from polar phases of β and γ. In this research, we reported fabrication of PVDF inkjet inks with enhanced β-phase crystallinity by incorporating barium titanate nanoparticles (BaTiO3). BaTiO3 not only acts as a nucleating agent to induce β-phase crystallinity, but it also improves the electric properties of PVDF through synergistic a ferroelectric polarization effect. PVDF-BaTiO3 nanocomposite inkjet inks with different BaTiO3 concentrations were prepared by wet ball milling coupled with bath ultrasonication. It was observed that the sample with 5 w% of BaTiO3 had the highest β-phase crystallinity, while in higher ratios overall crystallinity deteriorated progressively, leading to more amorphous structures. Full article
(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing)
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Open AccessReview
Comparative Study of Green and Synthetic Polymers for Enhanced Oil Recovery
Polymers 2020, 12(10), 2429; https://doi.org/10.3390/polym12102429 - 21 Oct 2020
Viewed by 190
Abstract
Several publications by authors in the field of petrochemical engineering have examined the use of chemically enhanced oil recovery (CEOR) technology, with a specific interest in polymer flooding. Most observations thus far in this field have been based on the application of certain [...] Read more.
Several publications by authors in the field of petrochemical engineering have examined the use of chemically enhanced oil recovery (CEOR) technology, with a specific interest in polymer flooding. Most observations thus far in this field have been based on the application of certain chemicals and/or physical properties within this technique regarding the production of 50–60% trapped (residual) oil in a reservoir. However, there is limited information within the literature about the combined effects of this process on whole properties (physical and chemical). Accordingly, in this work, we present a clear distinction between the use of xanthan gum (XG) and hydrolyzed polyacrylamide (HPAM) as a polymer flood, serving as a background for future studies. XG and HPAM have been chosen for this study because of their wide acceptance in relation to EOR processes. To this degree, the combined effect of a polymer’s rheological properties, retention, inaccessible pore volume (PV), permeability reduction, polymer mobility, the effects of salinity and temperature, and costs are all investigated in this study. Further, the generic screening and design criteria for a polymer flood with emphasis on XG and HPAM are explained. Finally, a comparative study on the conditions for laboratory (experimental), pilot-scale, and field-scale application is presented. Full article
(This article belongs to the Section Polymer Applications)
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Open AccessReview
Circular Intensity Differential Scattering for Label-Free Chromatin Characterization: A Review for Optical Microscopy
Polymers 2020, 12(10), 2428; https://doi.org/10.3390/polym12102428 - 21 Oct 2020
Viewed by 202
Abstract
Circular Intensity Differential Scattering (CIDS) provides a differential measurement of the circular right and left polarized light and has been proven to be a gold standard label-free technique to study the molecular conformation of complex biopolymers, such as chromatin. In early works, it [...] Read more.
Circular Intensity Differential Scattering (CIDS) provides a differential measurement of the circular right and left polarized light and has been proven to be a gold standard label-free technique to study the molecular conformation of complex biopolymers, such as chromatin. In early works, it has been shown that the scattering component of the CIDS signal gives information from the long-range chiral organization on a scale down to 1/10th–1/20th of the excitation wavelength, leading to information related to the structure and orientation of biopolymers in situ at the nanoscale. In this paper, we review the typical methods and technologies employed for measuring this signal coming from complex macro-molecules ordering. Additionally, we include a general description of the experimental architectures employed for spectroscopic CIDS measurements, angular or spectral, and of the most recent advances in the field of optical imaging microscopy, allowing a visualization of the chromatin organization in situ. Full article
(This article belongs to the Special Issue Biopolymers for Medicinal, Macromolecules, and Food Applications)
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Open AccessArticle
Laser-Induced Selective Electroless Plating on PC/ABS Polymer: Minimisation of Thermal Effects for Supreme Processing Speed
Polymers 2020, 12(10), 2427; https://doi.org/10.3390/polym12102427 - 21 Oct 2020
Viewed by 156
Abstract
The selective surface activation induced by laser (SSAIL) for electroless copper deposition on Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) blend is one of the promising techniques of electric circuit formation on free-shape dielectric surfaces, which broadens capabilities of 3D microscopic integrated devices (3D-MIDs). The process [...] Read more.
The selective surface activation induced by laser (SSAIL) for electroless copper deposition on Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) blend is one of the promising techniques of electric circuit formation on free-shape dielectric surfaces, which broadens capabilities of 3D microscopic integrated devices (3D-MIDs). The process consists of laser excitation, chemical activation of laser-excited areas by dipping in a liquid and electroless copper deposition of the laser-treated areas. The limiting factor in increasing throughput of the technology is a laser activation step. Laser writing is performed by modern galvanometric scanners which reach the scanning speed of several meters per second. However, adverse thermal effects on PC/ABS polymer surface abridge the high-speed laser writing. In this work, an investigation was conducted on how these thermal effects limit surface activation for selective metal deposition from the view of physics and chemistry. An advanced laser beam scanning technique of interlacing with precise accuracy and the pulse-on-demand technique was applied to overcome mentioned problems for fast laser writing. Initially, the modelling of transient heat conduction was performed. The results revealed a significant reduction in heat accumulation. Applied methods of laser writing allowed the overall processing rate to increase by up to 2.4 times. Surface morphology was investigated by a scanning electron microscope. Energy-dispersive X-ray spectroscopy was used to investigate the modification of atomic concentration on the surface after laser treatment. Experiments did not show a correlation between surface morphology and electroless plating on laser-treated areas. However, significant variation in the composition of the material was revealed depending on the surface activity for electroless plating. Full article
(This article belongs to the Special Issue Advances in Laser–Polymer Interaction for Functional Applications)
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Open AccessArticle
Multifunctional Hypercrosslinked Porous Organic Polymers Based on Tetraphenylethene and Triphenylamine Derivatives for High-Performance Dye Adsorption and Supercapacitor
Polymers 2020, 12(10), 2426; https://doi.org/10.3390/polym12102426 - 21 Oct 2020
Viewed by 186
Abstract
We successfully prepared two different classes of hypercrosslinked porous organic polymers (HPPs)—the tetraphenylethene (TPE) and (4-(5,6-Diphenyl-1H-Benzimidazol-2-yl)-triphenylamine (DPT) HPPs—through the Friedel−Crafts polymerization of tetraphenylethene and 4-(5,6-diphenyl-1H-benzimidazol-2-yl)-triphenylamine, respectively, with 1,4-bis(chloromethyl)benzene (Ph-2Cl) in the presence of anhydrous FeCl3 as a catalyst. Our porous materials exhibited [...] Read more.
We successfully prepared two different classes of hypercrosslinked porous organic polymers (HPPs)—the tetraphenylethene (TPE) and (4-(5,6-Diphenyl-1H-Benzimidazol-2-yl)-triphenylamine (DPT) HPPs—through the Friedel−Crafts polymerization of tetraphenylethene and 4-(5,6-diphenyl-1H-benzimidazol-2-yl)-triphenylamine, respectively, with 1,4-bis(chloromethyl)benzene (Ph-2Cl) in the presence of anhydrous FeCl3 as a catalyst. Our porous materials exhibited high BET surface areas (up to 1000 m2 g−1) and good thermal stabilities. According to electrochemical and dyes adsorption applications, the as-prepared DPT-HPP exhibited a high specific capacitance of 110 F g−1 at a current density of 0.5 A g−1, with an excellent cycling stability of over 2000 times at 10 A g−1. In addition, DPT-HPP showed a high adsorption capacity up to 256.40 mg g−1 for the removal of RhB dye from water. Full article
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Open AccessReview
A Mini-Review on Chitosan-Based Hydrogels with Potential for Sustainable Agricultural Applications
Polymers 2020, 12(10), 2425; https://doi.org/10.3390/polym12102425 - 21 Oct 2020
Viewed by 184
Abstract
Agriculture is an important sector of the economy, but this industry consumes significant amounts of water, which is a precious and limited natural resource. Irrigation techniques and efforts to mitigate water usage influence the growth, survival, and yield of crops. However, superabsorbent polymers [...] Read more.
Agriculture is an important sector of the economy, but this industry consumes significant amounts of water, which is a precious and limited natural resource. Irrigation techniques and efforts to mitigate water usage influence the growth, survival, and yield of crops. However, superabsorbent polymers in combination with fertilizers can be employed to obtain sustained release of nutrients and improved water retention capacity of the soil. Despite significant recent progress in this area involving synthetic polyacrylate hydrogels, there are no industrially applicable solutions exhibiting similar performance using natural biopolymers or synthetic polymers enriched with natural components. This review focuses on biodegradable chitosan-based hydrogels (both natural and semi-synthetic), and discusses their potential agricultural and horticultural applications. The methods for synthesizing hydrogels via physical or chemical crosslinking, and the resulting functional properties of recently reported hydrogels, such as water retention and release of active ingredients, are presented herein. Full article
(This article belongs to the Special Issue Functional Chitosan-Based Composites II)
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Open AccessArticle
Innovative Hyperbranched Polybenzoxazine-Based Graphene Oxide—Poly(amidoamines) Nanomaterials
Polymers 2020, 12(10), 2424; https://doi.org/10.3390/polym12102424 - 21 Oct 2020
Viewed by 156
Abstract
The covalent functionalization of graphene oxide (GO) surface with hyperbranched benzoxazine (BZ) structures has been achieved using poly(amidoamine) dendrimers (PAMAM) of different generations. By increasing the PAMAM generation, multiple benzoxazine rings were synthesized decorating the GO layers. The polymerization process and the exfoliation [...] Read more.
The covalent functionalization of graphene oxide (GO) surface with hyperbranched benzoxazine (BZ) structures has been achieved using poly(amidoamine) dendrimers (PAMAM) of different generations. By increasing the PAMAM generation, multiple benzoxazine rings were synthesized decorating the GO layers. The polymerization process and the exfoliation behavior were investigated. The novel BZ-functionalized GO hybrid materials were characterized by a combination of techniques such as FT-IR, XPS, and 1H-NMR for the confirmation of benzoxazine formation onto the GO layer surfaces. Raman and XRD investigation showed that the GO stacking layers are highly disintegrated upon functionalization with hyperbranched benzoxazine monomers, the exfoliation being more probably to occur when lower PAMAM generation (G) is involved for the synthesis of hybrid GO-BZ nanocomposites. The polymerization of BZ rings may occur either between the BZ units from the same dendrimer molecule or between BZ units from different dendrimer molecules, thus influencing the intercalation/exfoliation of GO. DSC data showed that the polymerization temperature strongly depends on the PAMAM generation and a significant decrease of this value occurred for PAMAM of higher generation, the polymerization temperature being reduced with ~10 °C in case of GO-PAMAM(G2)-BZ. Moreover, the nanoindentation measurements showed significant mechanical properties improvement in case of GO-PAMAM(G2)-BZ comparing to GO-PAMAM(G0)-BZ in terms of Young modulus (from 0.536 GPa to 1.418 GPa) and stiffness (from 3617 N/m to 9621 N/m). Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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Open AccessArticle
Poly (Dimethylsiloxane) Coating for Repellency of Polar and Non-Polar Liquids
Polymers 2020, 12(10), 2423; https://doi.org/10.3390/polym12102423 - 21 Oct 2020
Viewed by 184
Abstract
The wettability of poly (dimethylsiloxane) (PDMS) coating on plasma-treated glass was studied at room temperature using polar and non-polar liquids. The wettability was investigated regarding the liquids’ surface tensions (STs), dielectric constants (DCs) and solubility parameters (SPs). For polar liquids, the contact angle [...] Read more.
The wettability of poly (dimethylsiloxane) (PDMS) coating on plasma-treated glass was studied at room temperature using polar and non-polar liquids. The wettability was investigated regarding the liquids’ surface tensions (STs), dielectric constants (DCs) and solubility parameters (SPs). For polar liquids, the contact angle (CA) and contact angle hysteresis (CAH) are controlled by the DCs and non-polar liquids by the liquids’ STs. Solubility parameter difference between the PDMS and the liquids demonstrated that non-polar liquids possessed lower CAH. An empirical model that integrates the interfacial properties of liquid/PDMS has been composed. Accordingly, the difference between the SPs of PDMS and the liquid is the decisive factor affecting CAH, followed by the differences in DCs and STs. Moreover, the interaction between the DCs and the SPs is of importance to minimize CAH. It has been concluded that CAH, and not CA, is the decisive attribute for liquid repellency of PDMS coating. Full article
(This article belongs to the Special Issue Functional Coatings and Its Applications)
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Open AccessArticle
Study of High-Density Polyethylene (HDPE) Kinetics Modification Treated by Dielectric Barrier Discharge (DBD) Plasma
Polymers 2020, 12(10), 2422; https://doi.org/10.3390/polym12102422 - 21 Oct 2020
Viewed by 250
Abstract
In this work, the plasma was used in the dielectric barrier discharge (DBD) technique for modifying the high-density polyethylene (HDPE) surface. The treatments were performed via argon or oxygen, for 10 min, at a frequency of 820 Hz, voltage of 20 kV, 2 [...] Read more.
In this work, the plasma was used in the dielectric barrier discharge (DBD) technique for modifying the high-density polyethylene (HDPE) surface. The treatments were performed via argon or oxygen, for 10 min, at a frequency of 820 Hz, voltage of 20 kV, 2 mm distance between electrodes, and atmospheric pressure. The efficiency of the plasma was determined through the triple Langmuir probe to check if it had enough energy to promote chemical changes on the material surface. Physicochemical changes were diagnosed through surface characterization techniques such as contact angle, attenuated total reflection to Fourier transform infrared spectroscopy (ATR-FTIR), X-ray excited photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Plasma electronics temperature showed that it has enough energy to break or form chemical bonds on the material surface, impacting its wettability directly. The wettability test was performed before and after treatment through the sessile drop, using distilled water, glycerin, and dimethylformamide, to the profile of surface tensions by the Fowkes method, analyzing the contact angle variation. ATR-FTIR and XPS analyses showed that groups and bonds were altered or generated on the surface when compared with the untreated sample. The AFM showed a change in roughness, and this directly affected the increase of wettability. Full article
(This article belongs to the Special Issue Plasma Processes for Polymers)
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Open AccessArticle
Energy-Saving Electrospinning with a Concentric Teflon-Core Rod Spinneret to Create Medicated Nanofibers
Polymers 2020, 12(10), 2421; https://doi.org/10.3390/polym12102421 - 20 Oct 2020
Viewed by 276
Abstract
Although electrospun nanofibers are expanding their potential commercial applications in various fields, the issue of energy savings, which are important for cost reduction and technological feasibility, has received little attention to date. In this study, a concentric spinneret with a solid Teflon-core rod [...] Read more.
Although electrospun nanofibers are expanding their potential commercial applications in various fields, the issue of energy savings, which are important for cost reduction and technological feasibility, has received little attention to date. In this study, a concentric spinneret with a solid Teflon-core rod was developed to implement an energy-saving electrospinning process. Ketoprofen and polyvinylpyrrolidone (PVP) were used as a model of a poorly water-soluble drug and a filament-forming matrix, respectively, to obtain nanofibrous films via traditional tube-based electrospinning and the proposed solid rod-based electrospinning method. The functional performances of the films were compared through in vitro drug dissolution experiments and ex vivo sublingual drug permeation tests. Results demonstrated that both types of nanofibrous films do not significantly differ in terms of medical applications. However, the new process required only 53.9% of the energy consumed by the traditional method. This achievement was realized by the introduction of several engineering improvements based on applied surface modifications, such as a less energy dispersive air-epoxy resin surface of the spinneret, a free liquid guiding without backward capillary force of the Teflon-core rod, and a smaller fluid–Teflon adhesive force. Other non-conductive materials could be explored to develop new spinnerets offering good engineering control and energy savings to obtain low-cost electrospun polymeric nanofibers. Full article
(This article belongs to the Special Issue Functional Electrospun Nanofibers)
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Open AccessArticle
Development of 3D Bioactive Scaffolds through 3D Printing Using Wollastonite–Gelatin Inks
Polymers 2020, 12(10), 2420; https://doi.org/10.3390/polym12102420 - 20 Oct 2020
Viewed by 215
Abstract
The bioactivity of scaffolds represents a key property to facilitate the bone repair after orthopedic trauma. This study reports the development of biomimetic paste-type inks based on wollastonite (CS) and fish gelatin (FG) in a mass ratio similar to natural bone, as an [...] Read more.
The bioactivity of scaffolds represents a key property to facilitate the bone repair after orthopedic trauma. This study reports the development of biomimetic paste-type inks based on wollastonite (CS) and fish gelatin (FG) in a mass ratio similar to natural bone, as an appealing strategy to promote the mineralization during scaffold incubation in simulated body fluid (SBF). High-resolution 3D scaffolds were fabricated through 3D printing, and the homogeneous distribution of CS in the protein matrix was revealed by scanning electron microscopy/energy-dispersive X-ray diffraction analysis (SEM/EDX) micrographs. The bioactivity of the scaffold was suggested by an outstanding mineralization capacity revealed by the apatite layers deposited on the scaffold surface after immersion in SBF. The biocompatibility was demonstrated by cell proliferation established by MTT assay and fluorescence microscopy images and confirmed by SEM micrographs illustrating cell spreading. This work highlights the potential of the bicomponent inks to fabricate 3D bioactive scaffolds and predicts the osteogenic properties for bone regeneration applications. Full article
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Open AccessArticle
A Non-Enzymatic Sensor Based on Fc-CHIT/[email protected] Nanohybrids for Electrochemical Detection of Glucose
Polymers 2020, 12(10), 2419; https://doi.org/10.3390/polym12102419 - 20 Oct 2020
Viewed by 228
Abstract
Herein, a composite structure, consisting of Cu nanoparticles (NPs) deposited onto carbon nanotubes and modified with ferrocene-branched chitosan, was prepared in order to develop a nonenzymatic electrochemical glucose biosensor ferrocene-chitosan/carbon [email protected] Cu (Fc-CHIT/[email protected]). The elemental composition of the carbon nanohybrids, morphology and structure [...] Read more.
Herein, a composite structure, consisting of Cu nanoparticles (NPs) deposited onto carbon nanotubes and modified with ferrocene-branched chitosan, was prepared in order to develop a nonenzymatic electrochemical glucose biosensor ferrocene-chitosan/carbon [email protected] Cu (Fc-CHIT/[email protected]). The elemental composition of the carbon nanohybrids, morphology and structure were characterized by various techniques. Electrochemical impedance spectroscopy (EIS) was used to study the interfacial properties of the electrodes. Cyclic voltammetry (CV) and chronoamperometry methods in alkaline solution were used to determine glucose biosensing properties. The synergy effect of Cu NPs and Fc on current responses of the developed electrode resulted in good glucose sensitivity, including broad linear detection between 0.2 mM and 22 mM, a low detection limit of 13.52 μM and sensitivity of 1.256 μA mM−1cm−2. Moreover, the modified electrode possessed long-term stability and good selectivity in the presence of ascorbic acid, dopamine and uric acid. The results indicated that this inexpensive electrode had potential application for non-enzymatic electrochemical glucose detection. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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Open AccessArticle
Highly Scattering Hierarchical Porous Polymer Microspheres with a High-Refractive Index Inorganic Surface for a Soft-Focus Effect
Polymers 2020, 12(10), 2418; https://doi.org/10.3390/polym12102418 - 20 Oct 2020
Viewed by 177
Abstract
Functional light scattering materials have received considerable attention in various fields including cosmetics and optics. However, a conventional approach based on optically active inorganic materials requires considerable synthetic effort and complicated dispersion processes for special refractive materials. Here, we report a simple and [...] Read more.
Functional light scattering materials have received considerable attention in various fields including cosmetics and optics. However, a conventional approach based on optically active inorganic materials requires considerable synthetic effort and complicated dispersion processes for special refractive materials. Here, we report a simple and effective fabrication strategy for highly scattering hierarchical porous polymer microspheres with a high-refractive index inorganic surface that mitigates the disadvantages of inorganic materials, producing organic-inorganic hybrid particles with an excellent soft-focus effect. Hierarchical organic-inorganic hybrid particles were synthesized using the simple physical mixing of porous poly (methyl methacrylate) (PMMA) microparticles with different pore sizes and regularities as the organic core and titanium dioxide (TiO2) nanoparticles with different particle sizes as the inorganic shell. The polar noncovalent interactions between polar PMMA microspheres and the polar surface of TiO2 nanoparticles could induce the hierarchical core-shell structure of hybrid particles. The synthesized hybrid particles had increased diffuse reflectance properties of up to 160% compared with single inorganic particles. In addition, the light scattering efficiency and soft-focus effect could be increased further, depending on the size of the TiO2 nanoparticles and the pore characteristics of the PMMA microspheres. The proposed study can provide a facile and versatile way to improve the light scattering performance for potential cosmetics. Full article
(This article belongs to the Special Issue Hybrid Polymeric Materials II)
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Open AccessReview
Alginate: From Food Industry to Biomedical Applications and Management of Metabolic Disorders
Polymers 2020, 12(10), 2417; https://doi.org/10.3390/polym12102417 - 20 Oct 2020
Viewed by 205
Abstract
Initially used extensively as an additive and ingredient in the food industry, alginate has become an important compound for a wide range of industries and applications, such as the medical, pharmaceutical and cosmetics sectors. In the food industry, alginate has been used to [...] Read more.
Initially used extensively as an additive and ingredient in the food industry, alginate has become an important compound for a wide range of industries and applications, such as the medical, pharmaceutical and cosmetics sectors. In the food industry, alginate has been used to coat fruits and vegetables, as a microbial and viral protection product, and as a gelling, thickening, stabilizing or emulsifying agent. Its biocompatibility, biodegradability, nontoxicity and the possibility of it being used in quantum satis doses prompted scientists to explore new properties for alginate usage. Thus, the use of alginate has been expanded so as to be directed towards the pharmaceutical and biomedical industries, where studies have shown that it can be used successfully as biomaterial for wound, hydrogel, and aerogel dressings, among others. Furthermore, the ability to encapsulate natural substances has led to the possibility of using alginate as a drug coating and drug delivery agent, including the encapsulation of probiotics. This is important considering the fact that, until recently, encapsulation and coating agents used in the pharmaceutical industry were limited to the use of lactose, a potentially allergenic agent or gelatin. Obtained at a relatively low cost from marine brown algae, this hydrocolloid can also be used as a potential tool in the management of diabetes, not only as an insulin delivery agent but also due to its ability to improve insulin resistance, attenuate chronic inflammation and decrease oxidative stress. In addition, alginate has been recognized as a potential weight loss treatment, as alginate supplementation has been used as an adjunct treatment to energy restriction, to enhance satiety and improve weight loss in obese individuals. Thus, alginate holds the promise of an effective product used in the food industry as well as in the management of metabolic disorders such as diabetes and obesity. This review highlights recent research advances on the characteristics of alginate and brings to the forefront the beneficial aspects of using alginate, from the food industry to the biomedical field. Full article
(This article belongs to the Special Issue Biopolymers for Medicinal, Macromolecules, and Food Applications)
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Open AccessArticle
Proper Blends of Biodegradable Polycaprolactone and Natural Rubber for 3D Printing
Polymers 2020, 12(10), 2416; https://doi.org/10.3390/polym12102416 - 20 Oct 2020
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Abstract
Flexible thermoplastic elastomers (TPE) were prepared for fused deposition modeling (FDM) or 3D printing. These materials can be used for medical purposes such as disposable soft splints and other flexible devices. Blends of 50% epoxidized natural rubber (ENR-50) and block rubber (Standard Thai [...] Read more.
Flexible thermoplastic elastomers (TPE) were prepared for fused deposition modeling (FDM) or 3D printing. These materials can be used for medical purposes such as disposable soft splints and other flexible devices. Blends of 50% epoxidized natural rubber (ENR-50) and block rubber (Standard Thai Rubber 5L (STR5L)) with polycaprolactone (PCL) were produced and compared. The purpose of this study was to investigate the properties of natural rubber (NR) and PCL in simple blends with PCL contents of 40%, 50%, and 60% by weight (except at 75% for morphology study) in the base mixture (NR/PCL). The significant flow factors for FDM materials, such as melting temperature (Tm) and melt flow rate (MFR), were observed by differential scanning calorimetry (DSC) and via the melt flow index (MFI). In addition, the following mechanical properties were also determined: tensile strength, compression set, and hardness. The results from DSC showed that the melting temperature changed slightly (1–2 °C) with amount of PCL used, and there was a suspicious point in the 50/50 blends with both types of rubber. The lowest melting enthalpy of both blends was found at the 50/50 blended composition. The MFI results showed that PCL significantly affected the melt flow rate of both blends. The ENR-50/PCL blend flowed better than the STR5L/PCL blend. The conclusion was that this was due to the morphology of its phase structure having better uniformity than that of the STR5L/PCL blend. In compression set testing or measuring shape recovery, rubber directly influenced the recovery in all blends. The ENR-50/PCL blend had less recovery than the STR5L/PCL blend, probably due to the functional effects of epoxide groups and polarity mismatch. The hard phase PCL significantly affected the hardness of samples but improved shape recovery of the material. The ENR-50/PCL blend had better tensile properties than the STR5L/PCL blend. The elongation at break of both blends improved with a high rubber content. Hence, the ENR-50/PCL blend was superior to STR5L/PCL for printing purposes due to its better miscibility, uniformity, and flow, which are the keys to success for optimizing the fused deposition modeling conditions as well as the overall mechanical properties of products. Most blends in this study were only slightly different, but the 50/50 blend of ENR-50/PCL seemed to be near optimal for 3D printing. Full article
(This article belongs to the Section Polymer Applications)
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Open AccessReview
ON/OFF Switchable Nanocomposite Membranes for Separations
Polymers 2020, 12(10), 2415; https://doi.org/10.3390/polym12102415 - 20 Oct 2020
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Abstract
Although water, air, and other resources are abundant on earth, they have been subjected to strict environmental regulations. This is because of their limitation of availability for human consumption. In the separation industry, the membrane system was introduced to increase the amount of [...] Read more.
Although water, air, and other resources are abundant on earth, they have been subjected to strict environmental regulations. This is because of their limitation of availability for human consumption. In the separation industry, the membrane system was introduced to increase the amount of resources available to mankind. Experts used an easy-to-use polymeric material to design several membranes with porous structures for wastewater treatment, gas separation, and chemical removal; consequently, they succeeded in obtaining positive results. However, past polymeric membranes exhibited a chronic drawback such that it was difficult to simultaneously augment the permeate flux and improve its selectivity toward certain substances. Because of the trade-off relationship that existed between permeability and selectivity, the membrane efficiency was not very good; consequently, the cost-effectiveness was significantly hindered because there was no other alternative than to replace the membrane in order to maintain its initial characteristics steadily. This review begins with the introduction of a polymer nanocomposite (PNC) membrane that has been designed to solve the chronic problem of polymeric membranes; subsequently, the stimuli-responsive PNC membrane is elucidated, which has established itself as a popular topic among researchers in the separation industry for several decades. Furthermore, we have listed the different types and examples of stimuli-responsive PNC membranes, which can be switched by external stimuli, while discussing the future direction of the membrane separation industry. Full article
(This article belongs to the Special Issue Block Copolymers Particles: From Synthesis to Application)
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Open AccessArticle
Dielectric Spectroscopy and Thermal Properties of Poly(lactic) Acid Reinforced with Carbon-Based Particles: Experimental Study and Design Theory
Polymers 2020, 12(10), 2414; https://doi.org/10.3390/polym12102414 - 20 Oct 2020
Viewed by 193
Abstract
In the present study, polylactic acid (PLA) enriched with carbonaceous particles like multi-walled carbon nanotubes (MWCNTs), graphene nanoplates (GNPs) or a combination of both up 12 wt % of loading are used for producing 3D-printed specimens with fused deposition modeling (FDM) technology which [...] Read more.
In the present study, polylactic acid (PLA) enriched with carbonaceous particles like multi-walled carbon nanotubes (MWCNTs), graphene nanoplates (GNPs) or a combination of both up 12 wt % of loading are used for producing 3D-printed specimens with fused deposition modeling (FDM) technology which are then experimentally and theoretically investigated. The goal is to propose a non-conventional filaments indicated for additive manufacturing process with improved dielectric and thermal properties, compared to the performances exhibited by the unfilled polymer. In the light of the above, a wide dielectric spectroscopy and a thermal analysis, supported by a morphological investigation, are performed. The results highlight that the introduction of 1-dimensional filler (MWCNTs) are more suitable for improving the dielectric properties of the resulting materials, due to the enhancement of the interfacial polarization and the presence of functionalized groups, whereas 2-dimensional nanoparticles (GNPs) better favor the thermal conduction mechanisms thanks to the lower thermal boundary resistance between the two phases, polymer/filler. In particular, with a loading of 12 wt % of MWCNTs the relative permittivity reaches the value of 5.35 × 103 much greater than that of 3.7 measured for unfilled PLA while for the thermal conductivity the enhancement with 12 wt % of GNPs is about 261% respect the thermal behavior of the neat polymer. The experimental results are correlated to theoretical findings, whereas a design of experiment (DoE) approach is adopted for investigating how the different fillers influence the dielectric and thermal performances of the 3D-printed parts, thus assisting the design of such innovative materials that appear promising for development and applications in the electromagnetic (EM) field and heat transfer. Full article
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Open AccessArticle
Electrospun Multiple-Chamber Nanostructure and Its Potential Self-Healing Applications
Polymers 2020, 12(10), 2413; https://doi.org/10.3390/polym12102413 - 20 Oct 2020
Viewed by 214
Abstract
To address the life span of materials in the process of daily use, new types of structural nanofibers, fabricated by multifluid electrospinning to encapsulate both epoxy resin and amine curing agent, were embedded into an epoxy matrix to provide it with self-healing ability. [...] Read more.
To address the life span of materials in the process of daily use, new types of structural nanofibers, fabricated by multifluid electrospinning to encapsulate both epoxy resin and amine curing agent, were embedded into an epoxy matrix to provide it with self-healing ability. The nanofibers, which have a polyacrylonitrile sheath holding two separate cores, had an average diameter of 300 ± 140 nm with a uniform size distribution. The prepared fibers had a linear morphology with a clear three-chamber inner structure, as verified by scanning electron microscope and transmission electron microscope images. The two core sections were composed of epoxy and amine curing agents, respectively, as demonstrated under the synergistic characterization of Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry. The TGA results disclosed that the core-shell nanofibers contained 9.06% triethylenetetramine and 20.71% cured epoxy. In the electrochemical corrosion experiment, self-healing coatings exhibited an effective anti-corrosion effect, unlike the composite without nanofibers. This complex nanostructure was proven to be an effective nanoreactor, which is useful to encapsulate reactive fluids. This engineering process by multiple-fluid electrospinning is the first time to prove that this special multiple-chamber structure has great potential in the field of self-healing. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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Open AccessArticle
Influence of the Ultrasonic Treatment on the Properties of Polybutylene Adipate Terephthalate, Modified by Antimicrobial Additive
Polymers 2020, 12(10), 2412; https://doi.org/10.3390/polym12102412 - 19 Oct 2020
Viewed by 230
Abstract
Particular attention is paid to biodegradable materials from the environmental point of view and antimicrobial materials that ensure the microbiological safety of packaged products. The aim of the work was to study the properties of the composition, based on biodegradable polybutylene adipate terephthalate [...] Read more.
Particular attention is paid to biodegradable materials from the environmental point of view and antimicrobial materials that ensure the microbiological safety of packaged products. The aim of the work was to study the properties of the composition, based on biodegradable polybutylene adipate terephthalate (PBAT) and the antimicrobial additive—birch bark extract (BBE). Test samples of materials were obtained on the laboratory extruder by extrusion with ultrasonic treatment of the melt. The concentration of the antimicrobial additive in the polymer matrix was 1 wt %. A complex research was carried out to study the structural, physico–mechanical characteristics, antimicrobial properties and biodegradability of the modified PBAT. Comparative assessment of the physico–mechanical characteristics of samples based on PBAT showed that the strength and elongation at break indices slightly decrease when the ultrasonic treatment of the melt is introduced. It was found out, that the antimicrobial additive in the composition of the polymer matrix at the concentration of 1 wt % has a static effect on the development of microorganisms on the surface of the studied modified films. Studies of the biodegradability of modified PBAT by composting for 4 months have shown that the decomposition period of modified materials increased, compared to pure PBAT. The developed modified polymer material can be recommended as an alternative replacement for materials based on polyethylene for food packaging. Full article
(This article belongs to the Special Issue Polymeric Materials for Food Packaging)
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Open AccessCommunication
Electric Heating Behavior of Reduced Oxide Graphene/Carbon Nanotube/Natural Rubber Composites with Macro-Porous Structure and Segregated Filler Network
Polymers 2020, 12(10), 2411; https://doi.org/10.3390/polym12102411 - 19 Oct 2020
Viewed by 166
Abstract
Conductive polymer composites with carbonaceous fillers are very attractive and play a significant role in the field of electric heaters owing to their lightweight, corrosion resistance, and easy processing as well as low manufacturing cost. In this study, lightweight reduced oxide graphene/carbon nanotube/natural [...] Read more.
Conductive polymer composites with carbonaceous fillers are very attractive and play a significant role in the field of electric heaters owing to their lightweight, corrosion resistance, and easy processing as well as low manufacturing cost. In this study, lightweight reduced oxide graphene/carbon nanotube/natural rubber (rGO/CNT/NR) composites were fabricated by a facile and cost-effective approach, which consists of rGO assembling on rubber latex particles and hydrogels formation due to the interaction network established between carbonaceous fillers and subsequent mild-drying of the resulting hydrogels. Thanks to the amphiphilic nature of GO sheets, which can serve as a surfactant, the hydrophobic CNTs were easily dispersed into water under ultrasound. On the basis of both the high stable rGO and CNTs suspension and the assembling of rGO on rubber latex, a three-dimensional segregated network of CNT and rGO were easily constructed in macro-porous composites. Either the segregated network and macro-porous structure endowed the resulting composites with low density (0.45 g cm−3), high electrical conductivity (0.60 S m−1), and excellent electric heating behavior, when the weight content of rGO and CNTs are 0.5% and 2.5%, respectively. For electric heating behavior, the steady-state temperature of the above composites reaches 69.1 °C at an input voltage of 15 V. Full article
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Open AccessArticle
Enhanced Heat Resistance of Acrylic Pressure-Sensitive Adhesive by Incorporating Silicone Blocks Using Silicone-Based Macro-Azo-Initiator
Polymers 2020, 12(10), 2410; https://doi.org/10.3390/polym12102410 - 19 Oct 2020
Viewed by 219
Abstract
To improve the heat resistance of acrylic-based pressure-sensitive adhesive (PSA), silicone-block-containing acrylic PSAs (SPSAs) were synthesized using a polydimethylsiloxane (PDMS)-based macro-azo-initiator (MAI). To evaluate the heat resistance of the PSA films, the probe tack and 90° peel strength were measured at different temperatures. [...] Read more.
To improve the heat resistance of acrylic-based pressure-sensitive adhesive (PSA), silicone-block-containing acrylic PSAs (SPSAs) were synthesized using a polydimethylsiloxane (PDMS)-based macro-azo-initiator (MAI). To evaluate the heat resistance of the PSA films, the probe tack and 90° peel strength were measured at different temperatures. The acrylic PSA showed that its tack curves changed from balanced debonding at 25 °C to cohesive debonding at 50 °C and exhibited a sharp decrease. However, in the case of SPSA containing 20 wt% MAI (MAI20), the balanced debonding was maintained at 75 °C, and its tack value hardly changed with temperature. As the MAI content increased, the peel strength at 25 °C decreased due to the microphase separation between PDMS- and acryl-blocks in SPSA, but the shear adhesion failure temperature (SAFT) increased almost linearly from 41.3 to 122.8 °C. Unlike stainless steel substrate, SPSA showed improved peel strength on a polypropylene substrate due to its low surface energy caused by PDMS block. Owing to the addition of 20 wt% silicone-urethane dimethacrylate oligomer and 200 mJ/cm2 UV irradiation dose, MAI20 showed significantly increased 90° peel strength at 25 °C (548.3 vs. 322.4 gf/25 mm for pristine MAI20). Its heat resistance under shear stress assessed by shear adhesion failure test (SAFT) exhibited raising in failure temperature to 177.3 °C when compared to non-irradiated sample. Full article
(This article belongs to the Special Issue Next-Generation Convergence Industry and Adhesives)
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Open AccessArticle
Investigation of Interface Thermal Resistance between Polymer and Mold Insert in Micro-Injection Molding by Non-Equilibrium Molecular Dynamics
Polymers 2020, 12(10), 2409; https://doi.org/10.3390/polym12102409 - 19 Oct 2020
Viewed by 212
Abstract
Micro-injection molding has attracted a wide range of research interests to fabricate polymer products with nanostructures for its advantages of cheap and fast production. The heat transfer between the polymer and the mold insert is important to the performance of products. In this [...] Read more.
Micro-injection molding has attracted a wide range of research interests to fabricate polymer products with nanostructures for its advantages of cheap and fast production. The heat transfer between the polymer and the mold insert is important to the performance of products. In this study, the interface thermal resistance (ITR) between the polypropylene (PP) layer and the nickel (Ni) mold insert layer in micro-injection molding was studied by using the method of non-equilibrium molecular dynamics (NEMD) simulation. The relationships among the ITR, the temperature, the packing pressure, the interface morphology, and the interface interaction were investigated. The simulation results showed that the ITR decreased obviously with the increase of the temperature, the packing pressure and the interface interaction. Both rectangle and triangle interface morphologies could enhance the heat transfer compared with the smooth interface. Moreover, the ITR of triangle interface was higher than that of rectangle interface. Based on the analysis of phonon density of states (DOS) for PP-Ni system, it was found that the mismatch between the phonon DOS of the PP atoms and Ni atoms was the main cause of the interface resistance. The frequency distribution of phonon DOS also affected the interface resistance. Full article
(This article belongs to the Section Polymer Processing and Performance)
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Open AccessArticle
Crystallization of Poly(ethylene)s with Regular Phosphoester Defects Studied at the Air–Water Interface
Polymers 2020, 12(10), 2408; https://doi.org/10.3390/polym12102408 - 19 Oct 2020
Viewed by 242
Abstract
Poly(ethylene) (PE) is a commonly used semi-crystalline polymer which, due to the lack of polar groups in the repeating unit, is not able to form Langmuir or Langmuir–Blodgett (LB) films. This problem can be solved using PEs with hydrophilic groups arranged at regular [...] Read more.
Poly(ethylene) (PE) is a commonly used semi-crystalline polymer which, due to the lack of polar groups in the repeating unit, is not able to form Langmuir or Langmuir–Blodgett (LB) films. This problem can be solved using PEs with hydrophilic groups arranged at regular distances within the polymer backbone. With acyclic diene metathesis (ADMET) polymerization, a tool for precise addition of polar groups after a certain interval of methylene sequence is available. In this study, we demonstrate the formation of Langmuir/LB films from two different PEs with regular phosphoester groups, acting as crystallization defects in the main chain. After spreading the polymers from chloroform solution on the water surface of a Langmuir trough and solvent evaporation, the surface pressure is recorded during compression under isothermal condition. These π-A isotherms, surface pressure π vs. mean area per repeat unit A, show a plateau zone at surface pressures of ~ (6 to 8) mN/m, attributed to the formation of crystalline domains of the PEs as confirmed by Brewster angle and epifluorescence microscopy. PE with ethoxy phosphoester defects (Ethoxy-PPE) forms circular shape domains, whereas Methyl-PPE-co-decadiene with methyl phosphoester defects and two different methylene sequences between the defects exhibits a film-like morphology. The domains/films are examined by atomic force microscopy after transferring them to a solid support. The thickness of the domains/films is found in the range from ~ (2.4 to 3.2) nm depending on the transfer pressure. A necessity of chain tilt in the crystalline domains is also confirmed. Grazing incidence X-ray scattering measurements in LB films show a single Bragg reflection at a scattering vector qxy position of ~ 15.1 nm−1 known from crystalline PE samples. Full article
(This article belongs to the Special Issue Phase Transitions in Polymers and Polymer Morphologies)
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Open AccessArticle
Effect of a Novel Flame Retardant on the Mechanical, Thermal and Combustion Properties of Poly(Lactic Acid)
Polymers 2020, 12(10), 2407; https://doi.org/10.3390/polym12102407 - 19 Oct 2020
Viewed by 219
Abstract
Poly(lactic) acid (PLA) is one of the most promising biobased materials, but its inherent flammability limits its applications. A novel flame retardant hexa-(DOPO-hydroxymethylphenoxy-dihydroxybiphenyl)-cyclotriphosphazene (HABP-DOPO) for PLA was prepared by bonding 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO) to cyclotriphosphazene. The morphologies, mechanical properties, thermal stability and burning behaviors [...] Read more.
Poly(lactic) acid (PLA) is one of the most promising biobased materials, but its inherent flammability limits its applications. A novel flame retardant hexa-(DOPO-hydroxymethylphenoxy-dihydroxybiphenyl)-cyclotriphosphazene (HABP-DOPO) for PLA was prepared by bonding 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO) to cyclotriphosphazene. The morphologies, mechanical properties, thermal stability and burning behaviors of PLA/HABP-DOPO blends were investigated using a scanning electron microscope (SEM), a universal mechanical testing machine, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI), vertical burning (UL-94) and a cone calorimeter test (CCT). The LOI value reached 28.5% and UL-94 could pass V-0 for the PLA blend containing 25 wt% HABP-DOPO. A significant improvement in fire retardant performance was observed for PLA/HABP-DOPO blends. PLA/HABP-DOPO blends exhibited balanced mechanical properties. The flame retardant mechanism of PLA/HABP-DOPO blends was evaluated. Full article
(This article belongs to the Section Polymer Chemistry)
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Open AccessArticle
EMG Measurement with Textile-Based Electrodes in Different Electrode Sizes and Clothing Pressures for Smart Clothing Design Optimization
Polymers 2020, 12(10), 2406; https://doi.org/10.3390/polym12102406 - 19 Oct 2020
Viewed by 206
Abstract
The surface electromyography (SEMG) is one of the most popular bio-signals that can be applied in health monitoring systems, fitness training, and rehabilitation devices. Commercial clothing embedded with textile electrodes has already been released onto the market, but there is insufficient information on [...] Read more.
The surface electromyography (SEMG) is one of the most popular bio-signals that can be applied in health monitoring systems, fitness training, and rehabilitation devices. Commercial clothing embedded with textile electrodes has already been released onto the market, but there is insufficient information on the performance of textile SEMG electrodes because the required configuration may differ according to the electrode material. The current study analyzed the influence of electrode size and pattern reduction rate (PRR), and hence the clothing pressure (Pc) based on in vivo SEMG signal acquisition. Bipolar SEMG electrodes were made in different electrode diameters Ø 5–30 mm, and the clothing pressure ranged from 6.1 to 12.6 mmHg. The results supported the larger electrodes, and Pc showed better SEMG signal quality by showing lower baseline noise and a gradual increase in the signal to noise ratio (SNR). In particular, electrodes, Ø ≥ 20 mm, and Pc ≥ 10 mmHg showed comparable performance to Ag-Ag/Cl electrodes in current textile-based electrodes. The current study emphasizes and discusses design factors that are particularly required in the designing and manufacturing process of smart clothing with SEMG electrodes, especially as an aspect of clothing design. Full article
(This article belongs to the collection Innovative Functional Textiles)
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Open AccessArticle
Removal of Cd2+ from Water by Use of Super-Macroporous Cryogels and Comparison to Commercial Adsorbents
Polymers 2020, 12(10), 2405; https://doi.org/10.3390/polym12102405 - 19 Oct 2020
Viewed by 160
Abstract
In this study amphoteric cryogels were synthesized by the use of free-radical co-polymerization of acrylate-based precursors (methacrylic acid and 2-acrylamido-2-methyl-1-propansulfonic acid) with allylamine at different ratios. The physico-chemical characteristics of the cryogels were examined using SEM/EDX, FT-IR, XPS and zeta potential measurements. The [...] Read more.
In this study amphoteric cryogels were synthesized by the use of free-radical co-polymerization of acrylate-based precursors (methacrylic acid and 2-acrylamido-2-methyl-1-propansulfonic acid) with allylamine at different ratios. The physico-chemical characteristics of the cryogels were examined using SEM/EDX, FT-IR, XPS and zeta potential measurements. The cryogels were tested toward Cd2+ removal from aqueous solutions at various pH and initial concentrations. Equilibrium studies revealed a maximum sorption capacity in the range of 132–249 mg/g. Leaching experiments indicated the stability of Cd2+ in the cryogel structure. Based on kinetics, equilibrium and characterization results, possible removal mechanisms are proposed, indicating a combination of ion exchange and complexation of Cd2+ with the cryogels’ surface functional groups. The cryogels were compared to commercially available adsorbents (zeolite Y and cation exchange resin) for the removal of Cd2+ from various water matrices (ultrapure water, tap water and river water) and the results showed that, under the experimental conditions used, the cryogels can be more effective adsorbents. Full article
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Open AccessReview
Gelatin Microsphere for Cartilage Tissue Engineering: Current and Future Strategies
Polymers 2020, 12(10), 2404; https://doi.org/10.3390/polym12102404 - 19 Oct 2020
Viewed by 261
Abstract
The gelatin microsphere (GM) provides an attractive option for tissue engineering due to its versatility, as reported by various studies. This review presents the history, characteristics of, and the multiple approaches to, the production of GM, and in particular, the water in oil [...] Read more.
The gelatin microsphere (GM) provides an attractive option for tissue engineering due to its versatility, as reported by various studies. This review presents the history, characteristics of, and the multiple approaches to, the production of GM, and in particular, the water in oil emulsification technique. Thereafter, the application of GM as a drug delivery system for cartilage diseases is introduced. The review then focusses on the emerging application of GM as a carrier for cells and biologics, and biologics delivery within a cartilage construct. The influence of GM on chondrocytes in terms of promoting chondrocyte proliferation and chondrogenic differentiation is highlighted. Furthermore, GM seeded with cells has been shown to have a high tendency to form aggregates; hence the concept of using GM seeded with cells as the building block for the formation of a complex tissue construct. Despite the advancement in GM research, some issues must still be addressed, particularly the improvement of GM’s ability to home to defect sites. As such, the strategy of intraarticular injection of GM seeded with antibody-coated cells is proposed. By addressing this in future studies, a better-targeted delivery system, that would result in more effective intervention, can be achieved. Full article
(This article belongs to the Section Polymer Applications)
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Open AccessReview
Antimicrobial Activities of Starch-Based Biopolymers and Biocomposites Incorporated with Plant Essential Oils: A Review
Polymers 2020, 12(10), 2403; https://doi.org/10.3390/polym12102403 - 19 Oct 2020
Viewed by 263
Abstract
Recently, many scientists and polymer engineers have been working on eco-friendly materials for starch-based food packaging purposes, which are based on biopolymers, due to the health and environmental issues caused by the non-biodegradable food packaging. However, to maintain food freshness and quality, it [...] Read more.
Recently, many scientists and polymer engineers have been working on eco-friendly materials for starch-based food packaging purposes, which are based on biopolymers, due to the health and environmental issues caused by the non-biodegradable food packaging. However, to maintain food freshness and quality, it is necessary to choose the correct materials and packaging technologies. On the other hand, the starch-based film’s biggest flaws are high permeability to water vapor transfer and the ease of spoilage by bacteria and fungi. One of the several possibilities that are being extensively studied is the incorporation of essential oils (EOs) into the packaging material. The EOs used in food packaging films actively prevent inhibition of bacteria and fungi and have a positive effect on food storage. This work intended to present their mechanical and barrier properties, as well as the antimicrobial activity of anti-microbacterial agent reinforced starch composites for extending product shelf life. A better inhibition of zone of antimicrobial activity was observed with higher content of essential oil. Besides that, the mechanical properties of starch-based polymer was slightly decreased for tensile strength as the increasing of essential oil while elongation at break was increased. The increasing of essential oil would cause the reduction of the cohesion forces of polymer chain, creating heterogeneous matrix and subsequently lowering the tensile strength and increasing the elongation (E%) of the films. The present review demonstrated that the use of essential oil represents an interesting alternative for the production of active packaging and for the development of eco-friendly technologies. Full article
(This article belongs to the Special Issue Biopolymers for Medicinal, Macromolecules, and Food Applications)
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