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Polymers, Volume 12, Issue 6 (June 2020) – 227 articles

Cover Story (view full-size image): One of the way to achieve highly efficient flame-retardant performance for polymer applications is the usage of synergistical multicomponent flame-retardant systems. Depending on the polymer used, multicomponent flame-retardant systems are required, whose reaction profiles are chemically tailor-made to efficiently counteract polymers’ decomposition pathway. In our paper, we show as an example how different particle sizes can change the decomposition pathway, leading to different effects in burning behavior. View this paper.
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Article
Glycerolized Li+ Ion Conducting Chitosan-Based Polymer Electrolyte for Energy Storage EDLC Device Applications with Relatively High Energy Density
Polymers 2020, 12(6), 1433; https://doi.org/10.3390/polym12061433 - 26 Jun 2020
Cited by 41 | Viewed by 2114
Abstract
In this study, the solution casting method was employed to prepare plasticized polymer electrolytes of chitosan (CS):LiCO2CH3:Glycerol with electrochemical stability (1.8 V). The electrolyte studied in this current work could be established as new materials in the fabrication of [...] Read more.
In this study, the solution casting method was employed to prepare plasticized polymer electrolytes of chitosan (CS):LiCO2CH3:Glycerol with electrochemical stability (1.8 V). The electrolyte studied in this current work could be established as new materials in the fabrication of EDLC with high specific capacitance and energy density. The system with high dielectric constant was also associated with high DC conductivity (5.19 × 10−4 S/cm). The increase of the amorphous phase upon the addition of glycerol was observed from XRD results. The main charge carrier in the polymer electrolyte was ion as tel (0.044) < tion (0.956). Cyclic voltammetry presented an almost rectangular plot with the absence of a Faradaic peak. Specific capacitance was found to be dependent on the scan rate used. The efficiency of the EDLC was observed to remain constant at 98.8% to 99.5% up to 700 cycles, portraying an excellent cyclability. High values of specific capacitance, energy density, and power density were achieved, such as 132.8 F/g, 18.4 Wh/kg, and 2591 W/kg, respectively. The low equivalent series resistance (ESR) indicated that the EDLC possessed good electrolyte/electrode contact. It was discovered that the power density of the EDLC was affected by ESR. Full article
(This article belongs to the Special Issue Polymers for Energy Storage and Conversion)
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Article
Enhanced Surface Energetics of CNT-Grafted Carbon Fibers for Superior Electrical and Mechanical Properties in CFRPs
Polymers 2020, 12(6), 1432; https://doi.org/10.3390/polym12061432 - 26 Jun 2020
Cited by 14 | Viewed by 1850
Abstract
Surface enhancement of components is vital for achieving superior properties in a composite system. In this study, carbon nanotubes (CNTs) were grown on carbon fiber (CF) substrates to improve the surface area and, in turn, increase the adhesion between epoxy-resin and CFs. Nickel [...] Read more.
Surface enhancement of components is vital for achieving superior properties in a composite system. In this study, carbon nanotubes (CNTs) were grown on carbon fiber (CF) substrates to improve the surface area and, in turn, increase the adhesion between epoxy-resin and CFs. Nickel (Ni) was used as the catalyst in CNT growth, and was coated on CF sheets via the electroplating method. Surface energetics of CNT-grown CFs and their work of adhesion with epoxy resin were measured. SEM and TEM were used to analyze the morphology of the samples. After the optimization of surface energetics by catalyst weight ratio (15 wt.% Ni), CF-reinforced plastic (CFRP) samples were prepared using the hand lay-up method. To validate the effect of chemical vapor deposition (CVD)-grown CNTs on CFRP properties, samples were also prepared where CNT powder was added to epoxy prior to reinforcement with Ni-coated CFs. CFRP specimens were tested to determine their electrical resistivity, flexural strength, and ductility index. The electrical resistivity of CNT-grown CFRP was found to be about 9 and 2.3 times lower than those of as-received CFRP and CNT-added Ni-CFRP, respectively. Flexural strength of CNT-grown Ni-CFRP was enhanced by 52.9% of that of as-received CFRP. Interestingly, the ductility index in CNT-grown Ni-CFRP was 40% lower than that of CNT-added Ni-CFRP. This was attributed to the tip-growth formation of CNTs and the breakage of Ni coating. Full article
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Article
Novel Polymeric Composite TPPS/s-PEEK Membranes for Low Relative Humidity PEFC
Polymers 2020, 12(6), 1431; https://doi.org/10.3390/polym12061431 - 26 Jun 2020
Cited by 3 | Viewed by 1066
Abstract
Composite membranes based on different wt percentages of meso-tetrakis-(4-sulfonatophenyl)porphyrin (TPPS) embedded in a medium sulfonation degree (50%) sulfonated poly(etheretherketone) (s-PEEK) were investigated. The successful introduction of porphyrin into the membranes and the characterization of its different species into the membrane ionic domains [...] Read more.
Composite membranes based on different wt percentages of meso-tetrakis-(4-sulfonatophenyl)porphyrin (TPPS) embedded in a medium sulfonation degree (50%) sulfonated poly(etheretherketone) (s-PEEK) were investigated. The successful introduction of porphyrin into the membranes and the characterization of its different species into the membrane ionic domains were carried out by spectroscopic techniques. Moreover, the effect of TPPS arrangement was investigated in terms of water retention, proton conductivity and fuel cell performance at low relative humidity (RH). It was found that the introduction of this porphyrin induces a variation of the chemical-physical parameters, such as ion exchange capacity (IEC), water up-take (Wup %) λ and proton concentration ([H+]), attributable to the interactions that occur between the sulfonic groups of the polymer and the nitrogen sites of TPPS. The TPPS, in its J-aggregated form, actively participates in the proton conduction mechanism, also maintaining the adequate water content in more drastic conditions (80 °C and 50% RH). A maximum power density value of 462 mW cm−2 was obtained for the s-PEEK membrane, with a 0.77 wt % content of TPPS. This evidence suggests that the presence of J-aggregates in the proton conduction channels maintains a good hydration, even if a drastic reduction of the RH of the reactant gases occurs, preventing the membrane from a dry-out effect. Full article
(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cell)
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Article
Manuka Honey Reduces NETosis on an Electrospun Template Within a Therapeutic Window
Polymers 2020, 12(6), 1430; https://doi.org/10.3390/polym12061430 - 26 Jun 2020
Cited by 10 | Viewed by 1383
Abstract
Manuka honey, a topical wound treatment used to eradicate bacteria, resolve inflammation, and promote wound healing, is a focus in the tissue engineering community as a tissue template additive. However, its effect on neutrophil extracellular trap formation (NETosis) on a tissue engineering template [...] Read more.
Manuka honey, a topical wound treatment used to eradicate bacteria, resolve inflammation, and promote wound healing, is a focus in the tissue engineering community as a tissue template additive. However, its effect on neutrophil extracellular trap formation (NETosis) on a tissue engineering template has yet to be examined. As NETosis has been implicated in chronic inflammation and fibrosis, the reduction in this response within the wound environment is of interest. In this study, Manuka honey was incorporated into electrospun templates with large (1.7–2.2 µm) and small (0.25–0.5 µm) diameter fibers at concentrations of 0.1%, 1%, and 10%. Template pore sizes and honey release profiles were quantified, and the effect on the NETosis response of seeded human neutrophils was examined through fluorescence imaging and myeloperoxidase (MPO) analysis. The incorporation of 0.1% and 1% Manuka honey decreased NETosis on the template surface at both 3 and 6 h, while 10% honey exacerbated the NETosis response. Additionally, 0.1% and 1% Manuka honey reduced the MMP-9 release of the neutrophils at both timepoints. These data indicate a therapeutic window for Manuka honey incorporation into tissue engineering templates for the reduction in NETosis. Future in vivo experimentation should be conducted to translate these results to a physiological wound environment. Full article
(This article belongs to the Special Issue Functional Electrospun Nanofibers)
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Article
Development of Polypropylene-Based Single-Polymer Composites With Blends of Amorphous Poly-Alpha-Olefin and Random Polypropylene Copolymer
Polymers 2020, 12(6), 1429; https://doi.org/10.3390/polym12061429 - 26 Jun 2020
Cited by 8 | Viewed by 1493
Abstract
We developed polypropylene-based single-polymer composites (PP-SPC) with blends of amorphous poly-alpha-olefin (APAO) and random polypropylene copolymer (rPP) as matrix material and polypropylene (PP) woven fabric as reinforcement. Our goal was to utilize the lower melting temperature of APAO/rPP blends to increase the consolidation [...] Read more.
We developed polypropylene-based single-polymer composites (PP-SPC) with blends of amorphous poly-alpha-olefin (APAO) and random polypropylene copolymer (rPP) as matrix material and polypropylene (PP) woven fabric as reinforcement. Our goal was to utilize the lower melting temperature of APAO/rPP blends to increase the consolidation of the composites and decrease the heat load of the PP reinforcement. We produced the composites by film-stacking at 160 °C, and characterized the composites with density, peel, static tensile and dynamic falling weight impact tests, and by scanning electron microscopy. The results indicate that consolidation can be enhanced by increasing the APAO content of the matrix. We found that the APAO content of 50% is optimal for tensile properties. With increasing APAO content, the perforation energy decreased, but even the well-consolidated composites showed very high perforation energy. In the case of a pure APAO matrix, fiber content can be increased up to 80 wt% without a severe loss of consolidation, resulting in good tensile properties. The PP-SPCs developed possessed excellent mechanical properties, and well-consolidated composites can be produced with APAO/rPP blends as a matrix with high fiber content. Full article
(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers II)
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Article
Effect of NaOH Treatment on the Flexural Modulus of Hemp Core Reinforced Composites and on the Intrinsic Flexural Moduli of the Fibers
Polymers 2020, 12(6), 1428; https://doi.org/10.3390/polym12061428 - 26 Jun 2020
Cited by 3 | Viewed by 1100
Abstract
This paper describes the potential of using hemp core waste in the composite industry. These lignocellulosic residues can be used to produce environmentally friendly and economically viable composites and improve the overall value chain of hemp production. To this purpose, hemp core residues [...] Read more.
This paper describes the potential of using hemp core waste in the composite industry. These lignocellulosic residues can be used to produce environmentally friendly and economically viable composites and improve the overall value chain of hemp production. To this purpose, hemp core residues were alkaline treated at different NaOH concentrations and then mechanically defibrated. Hemp core fibers were mixed with polypropylene and injection molded to obtain testing specimens. The effect of sodium hydroxide on the flexural modulus of composites was studied from macro and micro mechanical viewpoints. Results showed remarkable improvements in the flexural modulus due to the presence of hemp core fibers in the composites. At a 50 wt % of reinforcement content, increments around 239%, 250% and 257% were obtained for composites containing fibers treated at a 5, 7.5 and 10 wt % of NaOH, respectively. These results were comparable to those of wood composites, displaying the potential of hemp core residues. The intrinsic flexural modulus of the hemp core fibers was computed by means of micromechanical analysis and was calculated using the ratios between a fiber flexural modulus factor and a fiber tensile modulus factor. The results agreed with those obtained by using models such as Hirsch and Tsai–Pagano. Other micromechanical parameters were studied to fully understand the contribution of the phases. The relationship between the fibers’ intrinsic flexural and Young’s moduli was studied, and the differences between properties were attributed to stress distribution and materials’ anisotropy. Full article
(This article belongs to the Special Issue Cellulose Polymer Composites)
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Article
Ruthenium Decorated Polypyrrole Nanoparticles for Highly Sensitive Hydrogen Gas Sensors Using Component Ratio and Protonation Control
Polymers 2020, 12(6), 1427; https://doi.org/10.3390/polym12061427 - 26 Jun 2020
Cited by 3 | Viewed by 1157
Abstract
Despite being highly flammable at lower concentrations and causing suffocation at higher concentrations, hydrogen gas continues to play an important role in various industrial processes. Therefore, an appropriate monitoring system is crucial for processes that use hydrogen. In this study, we found a [...] Read more.
Despite being highly flammable at lower concentrations and causing suffocation at higher concentrations, hydrogen gas continues to play an important role in various industrial processes. Therefore, an appropriate monitoring system is crucial for processes that use hydrogen. In this study, we found a nanocomposite comprising of ruthenium nanoclusters decorated on carboxyl polypyrrole nanoparticles (Ru_CPPy) to be successful in detecting hydrogen gas through a simple sonochemistry method. We found that the morphology and density control of the ruthenium component increased the active surface area to the target analyte (hydrogen molecule). Carboxyl polypyrrole (CPPy) in the nanocomposite was protonated to increase the charge transfer rate during gas detection. This material-based sensor electrode was highly sensitive (down to 0.5 ppm) toward hydrogen gas and had a fast response and recovery time under ambient conditions. The sensing ability of the electrode was maintained up to 15 days without structure deformations. Full article
(This article belongs to the Special Issue Conductive Polymer Composites)
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Article
Preparation of RGO and Anionic Polyacrylamide Composites for Removal of Pb(II) in Aqueous Solution
Polymers 2020, 12(6), 1426; https://doi.org/10.3390/polym12061426 - 26 Jun 2020
Cited by 1 | Viewed by 943
Abstract
Graphene oxide (GO) have been reported as adsorbent materials, because its surface contains a large number of oxygen-containing groups, which provide masses of active sites. Nevertheless, it is difficult to separate GO from aqueous solution by conventional means after the end of the [...] Read more.
Graphene oxide (GO) have been reported as adsorbent materials, because its surface contains a large number of oxygen-containing groups, which provide masses of active sites. Nevertheless, it is difficult to separate GO from aqueous solution by conventional means after the end of the adsorption process. Therefore, ethylene diamine-reduced graphene oxide/anionic polyacrylamide (E-RGO/APAM), with a large quantity of adsorption sites and strong flocculation was prepared in this study. The composite E-RGO/APAM was characterized by Fourier transform infrared (FTIR), laser Raman spectrometer (IR), scanning electron microscope (SEM). The obtained results indicated that amino groups were successfully introduced into GO. Particle size test showed that the particle size of E-RGO/APAM is up to three micrometers, which can be separated from the water by conventional means, such as filtration and centrifugation, to avoid secondary pollution. The efficiency of E-RGO/APAM for removing Pb(II) was tested. The results showed that the process of adsorption of Pb(II) by E-RGO/APAM can be fitted by pseudo second order kinetic equation, indicating that the adsorption rate of the adsorbent depends on the chemisorption process, and the theoretical maximum adsorption amount of E-RGO/APAM is 400.8 mg/g. Based on these results, it can be stated that E-RGO/APAM is effective in the removal of Pb(II) from aqueous solutions, and provides a new method for the removal of heavy metal ions from industrial wastewater. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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Article
Towards a Deeper Understanding of Creep and Physical Aging Behavior of the Emulsion Polymer Isocyanate
Polymers 2020, 12(6), 1425; https://doi.org/10.3390/polym12061425 - 26 Jun 2020
Cited by 1 | Viewed by 1064
Abstract
Information of the relaxation behaviors of polymer film is crucial to judge the durability of emulsion polymer isocyanate (EPI) as a structural adhesive for bonding timber-based products. A sequence of tensile creep tests and free volume evaluation of the cured EPI adhesive films [...] Read more.
Information of the relaxation behaviors of polymer film is crucial to judge the durability of emulsion polymer isocyanate (EPI) as a structural adhesive for bonding timber-based products. A sequence of tensile creep tests and free volume evaluation of the cured EPI adhesive films during isothermal condition were carried out by dynamic mechanical analysis and positron annihilation lifetime spectroscopy, respectively. It is the first time to explore the creep response and physical aging of the EPI film, as well as associated microstructural evolution. The results indicate that the creep characteristics of the glassy EPI coating intimately depend upon the crosslinker and elapsed time, and the ideal momentary creep master curve can be constructed in terms of modified horizontal shifting method. Furthermore, the relaxation process is found to be dominated by vacancy diffusion mechanism. In addition, increasing the polymeric isocyanate content can significantly enhance the resistance to creep deformation of EPI films, but also accelerate the physical aging process. Due to a higher packing degree of pure polymer films, the EPI films with aqueous emulsified isocyanate exhibit much better relaxation resistance compared to that with general isocyanate crosslinker. Full article
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Article
Characterization and Application of Gelatin Films with Pecan Walnut and Shell Extract (Carya illinoiensis)
Polymers 2020, 12(6), 1424; https://doi.org/10.3390/polym12061424 - 26 Jun 2020
Cited by 7 | Viewed by 1300
Abstract
Phenolic compounds that come from natural products are a good option for minimizing lipid oxidation. It should be noted that these are not only introduced directly into the food, but also incorporated into edible biofilms. In contact with food, they extend its useful [...] Read more.
Phenolic compounds that come from natural products are a good option for minimizing lipid oxidation. It should be noted that these are not only introduced directly into the food, but also incorporated into edible biofilms. In contact with food, they extend its useful life by avoiding contact with other surface and preventing deterioration air, one of the main objectives. In particular, gelatin is a biopolymer that has a great potential due to its abundance, low cost and good film-forming capacity. The aim of this study has been to design and analyse gelatin films that incorporate bioactive compounds that come from the walnut and a by-product, the walnut shell. The results showed that mechanical and water vapor barrier properties of the developed films varied depending on the concentration of the walnut, shell and synthetic antioxidant. With increasing walnut concentration (15%) the permeability to water vapor (0.414 g·mm/m2·day·Pascal, g·mm/m2·day·Pa) was significantly lower than the control (5.0368 g·mm/m2·day·Pa). Furthermore, in the new films the elongation at the break and Young’s modulus decrease by six times with respect to the control. Films with pure gelatin cannot act as an antioxidant shield to prevent food oxidation, but adding pecan walnut (15% concentration) presents 30% inhibition of the DPPH stable radical. Furthermore, in the DSC, the addition of walnut (15 and 9% concentrations), showed the formation of big crystals; which could improve the thermal stability of gelatin films. The use of new gelatin films has shown good protection against the oxidation of beef patties, increasing the useful lifetime up to nine days, compared to the control (3–4 days), which opens up a big field to the commercialization of meat products with lower quantities of synthetic products. Full article
(This article belongs to the Special Issue Functional Gelatin)
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Article
High-Yield Lignocellulosic Fibers from Date Palm Biomass as Reinforcement in Polypropylene Composites: Effect of Fiber Treatment on Composite Properties
Polymers 2020, 12(6), 1423; https://doi.org/10.3390/polym12061423 - 26 Jun 2020
Cited by 8 | Viewed by 1143
Abstract
In this work, date palm waste (DPW) stemming from the annual pruning of date palm was used as reinforcing filler in polypropylene (PP) matrix at 40% w/w. Three pre-treatment routes were performed for the DPW, namely (i) defibration, (ii) soft [...] Read more.
In this work, date palm waste (DPW) stemming from the annual pruning of date palm was used as reinforcing filler in polypropylene (PP) matrix at 40% w/w. Three pre-treatment routes were performed for the DPW, namely (i) defibration, (ii) soft alkali treatment, and (iii) enzymatic treatment, to obtain date palm fibers (DPF) and to investigate the effect of each process on their chemical composition, which will ultimately affect the mechanical properties of the resulting composites. The enzymatic and alkali treatment, combined with maleated polypropylene (MAPP) as a coupling agent, resulted in a composite with higher strength and stiffness than the neat PP. The differences in the reinforcing effect were explained by the change in the morphology of DPF and their chemical surface composition according to the selected treatment of DPW. Enzymatic treatment maximized the tensile strength of the compound as a consequence of an improvement in the interfacial shear strength and the intrinsic resistance of the fibers. Full article
(This article belongs to the Special Issue Cellulose Polymer Composites)
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Erratum
Erratum: Facile Functionalization via Plasma-Enhanced Chemical Vapor Deposition for the Effective Filtration of Oily Aerosol. Polymers 2019, 11, 1490
Polymers 2020, 12(6), 1422; https://doi.org/10.3390/polym12061422 - 25 Jun 2020
Viewed by 785
Abstract
The authors wish to make a change to the published paper [...] Full article
(This article belongs to the Special Issue Wettabilities and Surface Properties of Polymer Materials)
Article
Chemoenzymatic Synthesis of D-Glucitol-Based Non-Ionic Amphiphilic Architectures as Nanocarriers
Polymers 2020, 12(6), 1421; https://doi.org/10.3390/polym12061421 - 25 Jun 2020
Cited by 3 | Viewed by 1238
Abstract
Newer non-ionic amphiphiles have been synthesized using biocompatible materials and by following a greener approach i.e., D-glucitol has been used as a template, and hydrophobic and hydrophilic segments were incorporated on it by using click chemistry. The hydrophilic segments in turn were [...] Read more.
Newer non-ionic amphiphiles have been synthesized using biocompatible materials and by following a greener approach i.e., D-glucitol has been used as a template, and hydrophobic and hydrophilic segments were incorporated on it by using click chemistry. The hydrophilic segments in turn were prepared from glycerol using an immobilized Candida antarctica lipase (Novozym-435)-mediated chemoenzymatic approach. Surface tension measurements and dynamic light scattering studies reflect the self-assembling behavior of the synthesized amphiphilic architectures in the aqueous medium. The results from UV-Vis and fluorescence spectroscopy establish the encapsulation of guests in the hydrophobic core of self-assembled amphiphilic architectures. The results of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay indicate that the amphiphiles are well tolerated by the used A549 cell lines at all tested concentrations. Full article
(This article belongs to the Special Issue Enzymatic Synthesis of Polymers)
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Article
Fabrication of Robust Superhydrophobic Surfaces with Dual-Curing Siloxane Resin and Controlled Dispersion of Nanoparticles
Polymers 2020, 12(6), 1420; https://doi.org/10.3390/polym12061420 - 25 Jun 2020
Cited by 7 | Viewed by 1578
Abstract
We developed a simple method for the fabrication of superhydrophobic surfaces on various substrates using spray coating. The fabrication method started with the blending of a modified hydrophobic siloxane binder, silica nanoparticles, and a volatile solvent by sonication. The mixture was spray-coated on [...] Read more.
We developed a simple method for the fabrication of superhydrophobic surfaces on various substrates using spray coating. The fabrication method started with the blending of a modified hydrophobic siloxane binder, silica nanoparticles, and a volatile solvent by sonication. The mixture was spray-coated on various surfaces such as slide glass, paper, metal and fabric, forming a rough surface comprising silica particles dispersed in a hydrophobic binder. Surface hydrophobicity was affected by the surface energy of the binder and the degree of roughness. Therefore, we realized a superhydrophobic surface by controlling these two factors. The hydrophobicity of the siloxane binder was determined by the treatment of fluorine silane; the roughness was controlled by the amount of coated materials and sonication time. Thus, using the spray coating method, we obtained a superhydrophobic surface that was mechanically durable, thermally stable, and chemically resistant. Full article
(This article belongs to the Special Issue Functional Polymer Coatings)
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Article
Heterogenized Imidazolium-Based Ionic Liquids in Pebax®Rnew. Thermal, Gas Transport and Antimicrobial Properties
Polymers 2020, 12(6), 1419; https://doi.org/10.3390/polym12061419 - 25 Jun 2020
Cited by 6 | Viewed by 1341
Abstract
Imidazolium-based ionic liquids (ILs) have interesting antimicrobial activity and their inclusion in a flexible film is ideal to take advantage of their properties in practical applications. Poly(ether-block-amide) (Pebax®Rnew) films were prepared by solution casting, loading two synthetized ILs (1-hexadecyl-3-methylimidazolium dimethyl-5-sulfoisophthalate [Hdmim][DMSIP], [...] Read more.
Imidazolium-based ionic liquids (ILs) have interesting antimicrobial activity and their inclusion in a flexible film is ideal to take advantage of their properties in practical applications. Poly(ether-block-amide) (Pebax®Rnew) films were prepared by solution casting, loading two synthetized ILs (1-hexadecyl-3-methylimidazolium dimethyl-5-sulfoisophthalate [Hdmim][DMSIP], IL1 and 1-octyloximethyl-3-methylimidazolium hexafluorophosphate [OOMmim][PF6], IL2) up to 5 wt.%. The ILs were characterized by 1H NMR and MALDI-TOF spectroscopy. The films were investigated for miscibility, morphology, wettability, spectral properties and gas transport. The films display a good thermal stability (>200 °C). Differential scanning calorimetry (DSC) proves phase separation in the blends, that is consistent with FTIR analysis and with the island-like surface morphology observed in the micrographs. Gas permeability tests revealed that the IL-loaded films are dense and poreless, keeping the selectivity of the polymer matrix with a somewhat lessened permeability owing to the impermeable ILs crystals. The film antimicrobial activity, evaluated against Gram-negative and Gram-positive bacterial strains, was correlated to the structure of the incorporated ILs. The smaller IL2 salt did not modify the hydrophobic nature of the neat polymer and was readily released from the films. Instead, IL1, having a longer alkyl chain in the cation, provided a promising antimicrobial activity with a good combination of hydrophilicity, permeability and thermal stability. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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Article
Eco Friendly Approach for Synthesis, Characterization and Biological Activities of Milk Protein Stabilized Silver Nanoparticles
Polymers 2020, 12(6), 1418; https://doi.org/10.3390/polym12061418 - 24 Jun 2020
Cited by 30 | Viewed by 1932
Abstract
Today, the overall occurrence of re-emerging and rising illnesses has been a serious load on economies as well as public health. Here, we describe a simple, nontoxic and eco-friendly method for the synthesis of milk protein (MP)-stabilized silver nanoparticles (MP-s-AgNPs) using ultrahigh-temperature full [...] Read more.
Today, the overall occurrence of re-emerging and rising illnesses has been a serious load on economies as well as public health. Here, we describe a simple, nontoxic and eco-friendly method for the synthesis of milk protein (MP)-stabilized silver nanoparticles (MP-s-AgNPs) using ultrahigh-temperature full cream milk. Highly stable AgNPs were prepared with a fair control over their size, without using any reducing or stabilizing agent, and their formation was attributed to the presence of the MP casein. Ag+ ion reduction was possibly caused by the MPs. The synthesized MP-s-AgNPs were characterized in detail by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering. MP-s-AgNPs showed inhibitory activity against both Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative microorganisms (Salmonella typhi and Escherichia coli). Moreover, MP-s-AgNPs were found to be more toxic to bacteria than to fungi (Aspergillus fumigatus, Aspergillus ochraceus and Penicillium chrysogenum). Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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Article
Thermodynamic Characterization of Free and Surface Water of Colloidal Unimolecular Polymer (CUP) Particles Utilizing DSC
Polymers 2020, 12(6), 1417; https://doi.org/10.3390/polym12061417 - 24 Jun 2020
Cited by 8 | Viewed by 1311
Abstract
Colloidal Unimolecular Polymer (CUP) particles are spheroidal, 3–9 nm with charged groups on the surface and a hydrophobic core, which offer a larger surface water fraction to improve the analysis of its characteristics. Differential scanning calorimetry (DSC) was performed to determine the characteristics [...] Read more.
Colloidal Unimolecular Polymer (CUP) particles are spheroidal, 3–9 nm with charged groups on the surface and a hydrophobic core, which offer a larger surface water fraction to improve the analysis of its characteristics. Differential scanning calorimetry (DSC) was performed to determine the characteristics of surface water. These properties include the amount of surface water, the layer thickness, density, specific heat of the surface water above and below the freezing point of water, melting point depression of free water, effect of charge density and particle size. The charge density on the CUP surface was varied as well as the molecular weight which controls the particle diameter. The surface water is proportional to the weight fraction of CUP <20%. Analogous to recrystallization the CUP particles were trapped in the ice when rapidly cooled but slow cooling excluded the CUP, causing inter-molecular counterion condensation and less surface water. The density of surface water was calculated to be 1.023 g/mL to 1.056 g/mL depending on the surface charge density. The thickness of surface water increased with surface charge density. The specific heat of surface water was found to be 3.04 to 3.07 J/g·K at 253.15 K and 3.07 to 3.09 J/g·K at 293.15 K. The average area occupied by carboxylate and ester groups on the CUP surface were determined. Full article
(This article belongs to the Special Issue Single-Chain Polymer Nanotechnology)
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Article
Dynamic Mussel-Inspired Chitin Nanocomposite Hydrogels for Wearable Strain Sensors
Polymers 2020, 12(6), 1416; https://doi.org/10.3390/polym12061416 - 24 Jun 2020
Cited by 11 | Viewed by 1914
Abstract
It is an ongoing challenge to fabricate an electroconductive and tough hydrogel with autonomous self-healing and self-recovery (SELF) for wearable strain sensors. Current electroconductive hydrogels often show a trade-off between static crosslinks for mechanical strength and dynamic crosslinks for SELF properties. In this [...] Read more.
It is an ongoing challenge to fabricate an electroconductive and tough hydrogel with autonomous self-healing and self-recovery (SELF) for wearable strain sensors. Current electroconductive hydrogels often show a trade-off between static crosslinks for mechanical strength and dynamic crosslinks for SELF properties. In this work, a facile procedure was developed to synthesize a dynamic electroconductive hydrogel with excellent SELF and mechanical properties from starch/polyacrylic acid (St/PAA) by simply loading ferric ions (Fe3+) and tannic acid-coated chitin nanofibers (TA-ChNFs) into the hydrogel network. Based on our findings, the highest toughness was observed for the 1 wt.% TA-ChNF-reinforced hydrogel (1.43 MJ/m3), which is 10.5-fold higher than the unreinforced counterpart. Moreover, the 1 wt.% TA-ChNF-reinforced hydrogel showed the highest resistance against crack propagation and a 96.5% healing efficiency after 40 min. Therefore, it was chosen as the optimized hydrogel to pursue the remaining experiments. Due to its unique SELF performance, network stability, superior mechanical, and self-adhesiveness properties, this hydrogel demonstrates potential for applications in self-wearable strain sensors. Full article
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Article
Facile Fabrication of High-Performance Thin Film Nanocomposite Desalination Membranes Imbedded with Alkyl Group-Capped Silica Nanoparticles
Polymers 2020, 12(6), 1415; https://doi.org/10.3390/polym12061415 - 24 Jun 2020
Cited by 10 | Viewed by 1249
Abstract
The advantages of thin film nanocomposite reverse osmosis (TFN-RO) membranes have been demonstrated by numerous studies within the last decade. This study proposes a facile and novel method to tune the microscale and nanoscale structures, which has good potential to fabricate high-performance TFN-RO [...] Read more.
The advantages of thin film nanocomposite reverse osmosis (TFN-RO) membranes have been demonstrated by numerous studies within the last decade. This study proposes a facile and novel method to tune the microscale and nanoscale structures, which has good potential to fabricate high-performance TFN-RO membranes. This method involves the addition of alkyl capped silica nanoparticles (alkyl-silica NPs) into the organic phase during interfacial polymerization (IP). We discovered for the first time that the high concentration alkyl-silica NPs in organic solvent isopar-G can limit the diffusion of MPD molecules at the interface, therefore shaping the intrinsic thickness and microstructures of the PA layer. Moreover, the alkyl group modification greatly reduces the NPs agglomeration and increases the compatibility between the NPs and the PA matrix. We further demonstrate that the doping of alkyl-silica NPs impacts the performance of the TFN-RO membrane by affecting intrinsic thickness, higher surface area, hydrophobic plugging effect, and higher surface charge by a series of characterization. At brackish water desalination conditions (2000 ppm NaCl, 1.55 MPa), the optimal brackish water flux was 55.3 L/m2∙h, and the rejection was maintained at 99.6%, or even exceeded this baseline. At seawater desalination conditions (32,000 ppm NaCl, 5.5 MPa), the optimized seawater flux reached 67.7 L/m2∙h, and the rejection was sustained at 99.4%. Moreover, the boron rejection was elevated by 11%, which benefits from a hydrophobic plugging effect of the alkyl groups. Full article
(This article belongs to the Special Issue Polymer Membranes for High Efficient Separation)
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Article
An Innovative Method for the Recycling of Waste Carbohydrate-Based Flours
Polymers 2020, 12(6), 1414; https://doi.org/10.3390/polym12061414 - 24 Jun 2020
Cited by 7 | Viewed by 1158
Abstract
This work represents an innovative study that, for the first time, explores the possibility to use waste flours to produce thermoplastic polymeric bio-films. To the best of our knowledge, this is the first time that waste flours, derived from bakeries, pizzerias or pasta [...] Read more.
This work represents an innovative study that, for the first time, explores the possibility to use waste flours to produce thermoplastic polymeric bio-films. To the best of our knowledge, this is the first time that waste flours, derived from bakeries, pizzerias or pasta factories, have been proposed for the production of bio-polymers, as a replacement of neat starch. To this aim, durum waste flour derived from a pasta factory, soft waste flour derived from pizzerias and neat maize starch used as control material were firstly analyzed from dimensional, morphological and chemical points of view. Afterwards, waste flour films were produced by the addition of a nature-based plasticizer, glycerol. Mechanical characterization of the plasticized thermoplastic films, produced by compression molding, evidenced low performances, even in the case of the neat maize starch. In order to improve the mechanical properties, the possibility to include polylactic acid and cardanol-based plasticizer was also investigated. Mass transport properties of all the produced bio-films were investigated by measuring their water vapor permeability and hygroscopic absorption. The durability properties of the bio-films were assessed by accelerated ageing tests, while the bio-degradability of the waste-based films was evaluated by measuring the solubility and the degradation in water. The physicochemical analyses of the novel bio-films evidenced good mechanical properties; specifically, the waste-based films showed a lower hygroscopic absorption and water solubility than those of the blends containing neat starch. Full article
(This article belongs to the Special Issue Eco-Innovative Engineering of the Polymer Material’s Life Cycle)
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Article
Hydrophilic Submicron Nanogel Particles for Specific Recombinant Proteins Extraction and Purification
Polymers 2020, 12(6), 1413; https://doi.org/10.3390/polym12061413 - 24 Jun 2020
Cited by 2 | Viewed by 1043
Abstract
In biomedical diagnosis and bionanotechnologies, the extraction and purification of proteins and protein derivatives are of great interest. In fact, to purify recombinant proteins for instance, new methodologies and well appropriate material supports need to be established and also to be evaluated. In [...] Read more.
In biomedical diagnosis and bionanotechnologies, the extraction and purification of proteins and protein derivatives are of great interest. In fact, to purify recombinant proteins for instance, new methodologies and well appropriate material supports need to be established and also to be evaluated. In this work, hydrophilic nanohydrogel particles were prepared for recombinant proteins extraction for purification purpose. The prepared nanohydrogel polymer-based particles are hydrophilic below the volume phase transition temperature (TVPT) and dehydrated above the TVPT, due to the thermally sensitive poly(N-alkyl acrylamide) and poly(N-alkyl methacrylamide) derivatives. Then, the use of heavy metal ions in the presence of such functional particles should specifically capture recombinant proteins (i.e., proteins bearing a poly(histidine) part). In order to understand and to optimize the specific capture and the purification of recombinant proteins, various parameters have been investigated as a systematic study. Firstly, the adsorption was investigated as a function of pH and protein concentration. According to high hydration of the prepared nanohydrogel, no marked adsorption was observed. Secondly, the effect of pH was investigated and found to be the driven parameter affecting the metal ions immobilization and the recombinant proteins complexation. As a result, high protein complexation was observed at basic pH compared to non-complexation at acidic pH medium. The immobilized proteins via complexation were released by changing the pH. This decomplexation seems to be effective but depends on fixation conditions and particle surface structure. Full article
(This article belongs to the Special Issue Polymers and Nanomaterials: Interactions and Applications)
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Article
A Highly Sensitive and Flexible Capacitive Pressure Sensor Based on a Porous Three-Dimensional PDMS/Microsphere Composite
Polymers 2020, 12(6), 1412; https://doi.org/10.3390/polym12061412 - 24 Jun 2020
Cited by 40 | Viewed by 2885
Abstract
In recent times, polymer-based flexible pressure sensors have been attracting a lot of attention because of their various applications. A highly sensitive and flexible sensor is suggested, capable of being attached to the human body, based on a three-dimensional dielectric elastomeric structure of [...] Read more.
In recent times, polymer-based flexible pressure sensors have been attracting a lot of attention because of their various applications. A highly sensitive and flexible sensor is suggested, capable of being attached to the human body, based on a three-dimensional dielectric elastomeric structure of polydimethylsiloxane (PDMS) and microsphere composite. This sensor has maximal porosity due to macropores created by sacrificial layer grains and micropores generated by microspheres pre-mixed with PDMS, allowing it to operate at a wider pressure range (~150 kPa) while maintaining a sensitivity (of 0.124 kPa−1 in a range of 0~15 kPa) better than in previous studies. The maximized pores can cause deformation in the structure, allowing for the detection of small changes in pressure. In addition to exhibiting a fast rise time (~167 ms) and fall time (~117 ms), as well as excellent reproducibility, the fabricated pressure sensor exhibits reliability in its response to repeated mechanical stimuli (2.5 kPa, 1000 cycles). As an application, we develop a wearable device for monitoring repeated tiny motions, such as the pulse on the human neck and swallowing at the Adam’s apple. This sensory device is also used to detect movements in the index finger and to monitor an insole system in real-time. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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Article
Structural, Impedance and Electrochemical Characteristics of Electrical Double Layer Capacitor Devices Based on Chitosan: Dextran Biopolymer Blend Electrolytes
Polymers 2020, 12(6), 1411; https://doi.org/10.3390/polym12061411 - 24 Jun 2020
Cited by 26 | Viewed by 1833
Abstract
This report presents the preparation and characterizations of solid biopolymer blend electrolyte films of chitosan as cationic polysaccharide and anionic dextran (CS: Dextran) doped with ammonium iodide (NH4I) to be utilized as electrolyte and electrode separator in electrical double-layer capacitor (EDLC) [...] Read more.
This report presents the preparation and characterizations of solid biopolymer blend electrolyte films of chitosan as cationic polysaccharide and anionic dextran (CS: Dextran) doped with ammonium iodide (NH4I) to be utilized as electrolyte and electrode separator in electrical double-layer capacitor (EDLC) devices. FTIR and XRD techniques were used to study the structural behavior of the films. From the FTIR band analysis, shifting and broadening of the bands were observed with increasing salt concentration. The XRD analysis indicates amorphousness of the blended electrolyte samples whereby the peaks underwent broadening. The analysis of the impedance spectra emphasized that incorporation of 40 wt.% of NH4I salt into polymer electrolyte exhibited a relatively high conductivity (5.16 × 10−3 S/cm). The transference number measurement (TNM) confirmed that ion (tion = 0.928) is the main charge carriers in the conduction process. The linear sweep voltammetry (LSV) revealed the extent of durability of the relatively high conducting film which was 1.8 V. The mechanism of charge storage within the fabricated EDLC has been explained to be fully capacitive behavior with no redox peaks appearance in the cyclic voltammogram (CV). From this findings, four important parameters of the EDLC; specific capacitance, equivalent series resistance, energy density and power density were calculated as 67.5 F/g, 160 ohm, 7.59 Wh/kg and 520.8 W/kg, respectively. Full article
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Article
Carbonization of Polydopamine-Coating Layers on Boron Nitride for Thermal Conductivity Enhancement in Hybrid Polyvinyl Alcohol (PVA) Composites
Polymers 2020, 12(6), 1410; https://doi.org/10.3390/polym12061410 - 24 Jun 2020
Cited by 11 | Viewed by 1794
Abstract
Inspired by mussel adhesion proteins, boron nitride (BN) particles coated with homogeneous polydopamine (BNPDA) were prepared, and through an annealing process, a carbonized PDA layer on the surface of BN was obtained, which exhibited a nanocrystalline graphite-like structure. The effect of carbonization of [...] Read more.
Inspired by mussel adhesion proteins, boron nitride (BN) particles coated with homogeneous polydopamine (BNPDA) were prepared, and through an annealing process, a carbonized PDA layer on the surface of BN was obtained, which exhibited a nanocrystalline graphite-like structure. The effect of carbonization of PDA coating layer on BN particles was characterized by various analytical techniques including SEM, TEM, Raman spectroscopy, and XPS. When the resulting particles were used as a thermally conductive filler for polyvinyl alcohol (PVA) composite films, enhanced thermal conductivity was observed compared to raw BN composite due to the ordered structure and improved solubility in water. Furthermore, the homogeneous dispersion of the filler and excellent flexibility of the modified composite film with 21 wt % filler may be attributed to compatibility with the PVA chain. As the whole fabrication process did not use toxic chemicals (mainly water was used as the solvent), it may contribute to green and sustainable chemistry. Full article
(This article belongs to the Special Issue Hybrid Polymeric Materials II)
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Article
The Competition of Termination and Shielding to Evaluate the Success of Surface-Initiated Reversible Deactivation Radical Polymerization
Polymers 2020, 12(6), 1409; https://doi.org/10.3390/polym12061409 - 23 Jun 2020
Cited by 8 | Viewed by 1268
Abstract
One of the challenges for brush synthesis for advanced bioinspired applications using surface-initiated reversible deactivation radical polymerization (SI-RDRP) is the understanding of the relevance of confinement on the reaction probabilities and specifically the role of termination reactions. The present work puts forward a [...] Read more.
One of the challenges for brush synthesis for advanced bioinspired applications using surface-initiated reversible deactivation radical polymerization (SI-RDRP) is the understanding of the relevance of confinement on the reaction probabilities and specifically the role of termination reactions. The present work puts forward a new matrix-based kinetic Monte Carlo platform with an implicit reaction scheme capable of evaluating the growth pattern of individual free and tethered chains in three-dimensional format during SI-RDRP. For illustration purposes, emphasis is on normal SI-atom transfer radical polymerization, introducing concepts such as the apparent livingness and the molecular height distribution (MHD). The former is determined based on the combination of the disturbing impact of termination (related to conventional livingness) and shielding of deactivated species (additional correction due to hindrance), and the latter allows structure-property relationships to be identified, starting at the molecular level in view of future brush characterization. It is shown that under well-defined SI-RDRP conditions the contribution of (shorter) hindered dormant chains is relevant and more pronounced for higher average initiator coverages, despite the fraction of dead chains being less. A dominance of surface-solution termination is also put forward, considering two extreme diffusion modes, i.e., translational and segmental. With the translational mode termination is largely suppressed and the living limit is mimicked, whereas with the segmental mode termination occurs more and the termination front moves upward alongside the polymer layer growth. In any case, bimodalities are established for the tethered chains both on the level of the chain length distribution and the MHD. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Review
3D-MID Technology for Surface Modification of Polymer-Based Composites: A Comprehensive Review
Polymers 2020, 12(6), 1408; https://doi.org/10.3390/polym12061408 - 23 Jun 2020
Cited by 11 | Viewed by 2049
Abstract
The three-dimensional molded interconnected device (3D-MID) has received considerable attention because of the growing demand for greater functionality and miniaturization of electronic parts. Polymer based composite are the primary choice to be used as substrate. These materials enable flexibility in production from macro [...] Read more.
The three-dimensional molded interconnected device (3D-MID) has received considerable attention because of the growing demand for greater functionality and miniaturization of electronic parts. Polymer based composite are the primary choice to be used as substrate. These materials enable flexibility in production from macro to micro-MID products, high fracture toughness when subjected to mechanical loading, and they are lightweight. This survey proposes a detailed review of different types of 3D-MID modules, also presents the requirement criteria for manufacture a polymer substrate and the main surface modification techniques used to enhance the polymer substrate. The findings presented here allow to fundamentally understand the concept of 3D-MID, which can be used to manufacture a novel polymer composite substrate. Full article
(This article belongs to the Special Issue Materials and Methods for New Technologies in Polymer Processing II)
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Article
Superior X-ray Radiation Shielding Effectiveness of Biocompatible Polyaniline Reinforced with Hybrid Graphene Oxide-Iron Tungsten Nitride Flakes
Polymers 2020, 12(6), 1407; https://doi.org/10.3390/polym12061407 - 23 Jun 2020
Cited by 27 | Viewed by 1823
Abstract
X-ray radiation is a harmful carcinogenic electromagnetic source that can adversely affect the health of living species and deteriorate the DNA of cells, thus it’s vital to protect vulnerable sources from them. To address this flaw, the conductive polymeric structure of polyaniline (PANi) [...] Read more.
X-ray radiation is a harmful carcinogenic electromagnetic source that can adversely affect the health of living species and deteriorate the DNA of cells, thus it’s vital to protect vulnerable sources from them. To address this flaw, the conductive polymeric structure of polyaniline (PANi) was reinforced with diverse filler loadings (i.e., 25 wt % and 50 wt %) of hybrid graphene oxide-iron tungsten nitride (ITN) flakes toward attenuation of X-ray beams and inhabitation of microorganisms’ growth. Primary characterizations confirmed the successful decoration of graphene oxide (GO) with interconnected and highly dense structure of iron tungsten nitride with a density of about 24.21 g·cm−3 and reinforcement of PANi with GO-ITN. Additionally, the outcome of evaluations showed the superior performance of developed shields, where a shield with 1.2 mm thickness containing 50 wt % GO-ITN showed 131.73% increase in the electrical conductivity (compared with neat PANi) along with 78.07%, 57.12%, and 44.99% decrease in the amplitude of the total irradiated X-ray waves at 30, 40, and 60 kVp tube voltages, respectively, compared with control X-ray dosage. More importantly, the developed shields not only showed non-toxic nature and improved the viability of cells, but also completely removed the selected microorganisms at a concentration of 1000 µg·mL−1. Full article
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Article
Solid-Contact Potentiometric Sensors Based on Stimulus-Responsive Imprinted Polymers for Reversible Detection of Neutral Dopamine
Polymers 2020, 12(6), 1406; https://doi.org/10.3390/polym12061406 - 23 Jun 2020
Cited by 8 | Viewed by 1255
Abstract
Herein, we present for the first time a novel potentiometric sensor based on the stimulus-responsive molecularly imprinted polymer (MIP) as a selective receptor for neutral dopamine determination. This smart receptor can change its capabilities to recognize according to external environmental stimuli. Therefore, MIP-binding [...] Read more.
Herein, we present for the first time a novel potentiometric sensor based on the stimulus-responsive molecularly imprinted polymer (MIP) as a selective receptor for neutral dopamine determination. This smart receptor can change its capabilities to recognize according to external environmental stimuli. Therefore, MIP-binding sites can be regenerated in the polymeric membrane by stimulating with stimulus after each measurement. Based on this effect, reversible detection of the analyte via potentiometric transduction can be achieved. MIPs based on 4-vinylphenylboronic acid as the functional monomer were prepared as the selective receptor. This monomer can successfully bind to dopamine via covalent binding and forming a five- or six-membered cyclic ester in a weakly alkaline aqueous solution. In acidic medium, the produced ester dissociates and regenerates new binding sites in the polymeric membrane. The proposed smart sensor exhibited fast response and good sensitivity towards dopamine with a limit of detection 0.15 µM over the linear range 0.2–10 µM. The selectivity pattern of the proposed ISEs was also evaluated and revealed an enhanced selectivity towards dopamine over several phenolic compounds. Constant-current chronopotentiometry is used for evaluating the short-term potential stability of the proposed ISEs. The obtained results confirm that the stimulus-responsive MIPs provide an attractive way towards reversible MIP-based electrochemical sensors designation. Full article
(This article belongs to the Section Polymer Applications)
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Article
Synthesis, Phase-Transition Behaviour, and Oil Adsorption Performance of Porous Poly(oligo(ethylene glycol) Alkyl Ether Acrylate) Gels
Polymers 2020, 12(6), 1405; https://doi.org/10.3390/polym12061405 - 23 Jun 2020
Cited by 4 | Viewed by 1705
Abstract
To probe the effects of pendant side-chain structures on the properties of porous thermoresponsive polymer gels, oligo(ethylene glycol) alkyl ether acrylates were polymerised in an aqueous medium under radical-mediated phase-separation conditions. The monomer structures varied according to the lengths and termini of [...] Read more.
To probe the effects of pendant side-chain structures on the properties of porous thermoresponsive polymer gels, oligo(ethylene glycol) alkyl ether acrylates were polymerised in an aqueous medium under radical-mediated phase-separation conditions. The monomer structures varied according to the lengths and termini of their ethylene glycol side chains. The porous poly(oligo(ethylene glycol) alkyl ether acrylate) (POEGA) gels exhibited variable lower critical solution temperatures (LCSTs) but similar and rapid swelling–deswelling behaviours. Although the LCST of the poly(tri(ethylene glycol) monomethyl ether acrylate) (PTEGA) gel decreased with increasing aqueous NaCl or CaCl2 concentration, PTEGA showed excellent thermosensitivity in highly concentrated salt solutions, recommending its application in saline environments. Examination of PTEGA adsorption performance in an oil–water emulsion showed that n-tridecane adsorption increased with temperature. Although n-tridecane was effectively adsorbed at 70 °C, its release from the fully adsorbed PTEGA gel was difficult despite a temperature reduction from 70 to 20 °C. Full article
(This article belongs to the Special Issue Thermoresponsive Polymers)
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Article
Innovation in Tigernut (Cyperus Esculentus L.) Milk Production: In Situ Hydrolysis of Starch
Polymers 2020, 12(6), 1404; https://doi.org/10.3390/polym12061404 - 23 Jun 2020
Cited by 6 | Viewed by 1918
Abstract
Tigernut tubers (Cyperus esculentus) are used for the production of vegetable milk, commonly known as “Horchata de chufa” in Spain. The presence of starch in the tuber limits the yield of the milk, since this carbohydrate gelatinizes during the pasteurization of [...] Read more.
Tigernut tubers (Cyperus esculentus) are used for the production of vegetable milk, commonly known as “Horchata de chufa” in Spain. The presence of starch in the tuber limits the yield of the milk, since this carbohydrate gelatinizes during the pasteurization of the milk and leads to the considerable solidification of this drink. The present work aims to improve the yields and extraction practice of the milk by an in situ hydrolysis of starch, using exogenous amylases of industrial or vegetable origin. The obtained results show that sprouting improves the extraction yields of tigernut milk, which goes from 50% to about 70%. This improvement in milk yield corresponds to a hydrolysis of about 35% of the starch in the tuber. The use of exogenous amylases leads to starch hydrolysis rates of 45% and 70%, respectively, for amylolytic extracts from sprouted tigernut tubers and amylase, with the corollary of a natural increase in the sweetness of milk. This technical approach makes it possible to produce a naturally sweetened tigernut milk which easily lends itself to pasteurization without a significant increase in viscosity. Full article
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