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Polymers, Volume 10, Issue 11 (November 2018)

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Open AccessArticle ZnO Quantum Dots Modified by pH-Activated Charge-Reversal Polymer for Tumor Targeted Drug Delivery
Polymers 2018, 10(11), 1272; https://doi.org/10.3390/polym10111272 (registering DOI)
Received: 25 October 2018 / Revised: 9 November 2018 / Accepted: 12 November 2018 / Published: 15 November 2018
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Abstract
In this paper, we reported a pH responsive nano drug delivery system (NDDS) based on ZnO quantum dots (QDs) for controlled release of drugs. Zwitterionic poly(carboxybetaine methacrylate) (PCBMA) and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) were introduced to modify ZnO QDs, which can help enhance
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In this paper, we reported a pH responsive nano drug delivery system (NDDS) based on ZnO quantum dots (QDs) for controlled release of drugs. Zwitterionic poly(carboxybetaine methacrylate) (PCBMA) and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) were introduced to modify ZnO QDs, which can help enhance water stability, increase blood circulation time, and promote endocytosis. After tuning of PCBMA/PDMAEMA ratios, the ZnO@P(CBMA-co-DMAEMA) nanoplatform shows a sensitive switch from strong protein adsorption resistance (with negatively charged surface) at physiological pH to strong adhesion to tumor cell membranes (with positively charged surface) at the slightly acidic extracellular pH of tumors. Anti-cancer drug, Doxorubicin (DOX), molecules were demonstrated to be successfully loaded to ZnO@P(CBMA-co-DMAEMA) with a relatively large drug loading content (24.6%). In addition, ZnO@P(CBMA-co-DMAEMA) loaded with DOX can achieve lysosomal acid degradation and release of DOX after endocytosis by tumor cells, resulting in synergistic treatment of cancer, which is attributed to a combination of the anticancer effect of Zn2+ and DOX. Full article
(This article belongs to the Special Issue Functionally Responsive Polymeric Materials II)
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Open AccessArticle Hybrid Materials Based on l,d-Poly(lactic acid) and Single-Walled Carbon Nanotubes as Flexible Substrate for Organic Devices
Polymers 2018, 10(11), 1271; https://doi.org/10.3390/polym10111271 (registering DOI)
Received: 9 October 2018 / Revised: 8 November 2018 / Accepted: 8 November 2018 / Published: 15 November 2018
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Abstract
We report on the application of l,d-poly(lactic acid) (l,d-PLA) with dispersed Single-Walled Carbon Nanotubes (SWCN) as a flexible translucent electrode for organic devices. We used commercially available nanotubes in various weight ratios from 0 to 8% dispersed in chloroform polymeric
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We report on the application of l,d-poly(lactic acid) (l,d-PLA) with dispersed Single-Walled Carbon Nanotubes (SWCN) as a flexible translucent electrode for organic devices. We used commercially available nanotubes in various weight ratios from 0 to 8% dispersed in chloroform polymeric solution by ultrasonication and were drop cast. The created hybrid materials were investigated by differential scanning calorimetry to determine the influence of SWCN content on the thermal behavior, while polarizing optical microscope was used to find the effect of mechanical deformations on the textures. Drop-cast films were studied by optical transmittance, conductivity, dielectric properties and by thermal imaging under applied potential. Thermal imaging provided evidence of visible voltage-activated conduction. Simple mechanical deformation such as bending with stretching at edge to ca. 90 and elongation test were performed. Moreover, interactions between l,d-poly(lactic acid) and SWCN were investigated by FT-IR and NMR spectroscopy. Finally, we can conclude that the thermographic examination of created films permits fast, simple and inexpensive localization of defects on the surface of l,d-PLA:SWCN film, together with the electrical properties of the films. Full article
(This article belongs to the Special Issue Polymer-CNT Nanocomposites)
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Open AccessArticle Thermal Properties of TiO2NP/CNT/LDPE Hybrid Nanocomposite Films
Polymers 2018, 10(11), 1270; https://doi.org/10.3390/polym10111270 (registering DOI)
Received: 14 October 2018 / Revised: 12 November 2018 / Accepted: 12 November 2018 / Published: 15 November 2018
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Abstract
This work aims to investigate the effect of hybrid filler concentration on the thermal stability of low-density polyethylene (LDPE) matrices. LDPE-based composite films were synthesized by melt mixing, followed by compression molding, to study the influence of titanium oxide nanoparticles (TONPs) and/or multi-walled
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This work aims to investigate the effect of hybrid filler concentration on the thermal stability of low-density polyethylene (LDPE) matrices. LDPE-based composite films were synthesized by melt mixing, followed by compression molding, to study the influence of titanium oxide nanoparticles (TONPs) and/or multi-walled carbon nanotubes (CNTs) on the thermal properties of LDPE matrices. Fourier transform infrared (FTIR) spectroscopy confirmed the slight increase in the band intensities after TONP addition and a remarkable surge after the incorporation of CNTs. The value of crystallization temperature (Tc) was not modified after incorporating TONPs, while an enhancement was observed after adding the hybrid fillers. The melting temperature (Tm) was not changed after introducing the CNTs and CNT/TONP hybrid fillers. The percentage crystallinity (Xc %) was increased by 4% and 6%, after incorporating 1 wt % and 3 wt % CNTs, respectively. The TONP incorporation did not modify the Xc %. Moreover, thermal gravimetric analysis (TGA) thermograms confirmed the increased thermal stability after introducing CNTs and hybrid fillers compared to TONP incorporation. Full article
(This article belongs to the Special Issue Thermal Properties and Applications of Polymers)
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Open AccessArticle Therapeutic Effect and Metabolic Mechanism of A Selenium-Polysaccharide from Ziyang Green Tea on Chronic Fatigue Syndrome
Polymers 2018, 10(11), 1269; https://doi.org/10.3390/polym10111269 (registering DOI)
Received: 8 October 2018 / Revised: 12 November 2018 / Accepted: 12 November 2018 / Published: 15 November 2018
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Abstract
Ziyang green tea was considered a medicine food homology plant to improve chronic fatigue Ssyndrome (CFS) in China. The aim of this research was to study the therapeutic effect of selenium-polysaccharides (Se-TP) from Ziyang green tea on CFS and explore its metabolic mechanism.
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Ziyang green tea was considered a medicine food homology plant to improve chronic fatigue Ssyndrome (CFS) in China. The aim of this research was to study the therapeutic effect of selenium-polysaccharides (Se-TP) from Ziyang green tea on CFS and explore its metabolic mechanism. A CFS-rats model was established in the present research and Se-TP was administrated to evaluate the therapeutic effect on CFS. Some serum metabolites including blood urea nitrogen (BUN), blood lactate acid (BLA), corticosterone (CORT), and aldosterone (ALD) were checked. Urine metabolites were analyzed via gas chromatography-mass spectrometry (GC-MS). Multivariate statistical analysis was also used to check the data. The results selected biomarkers that were entered into the MetPA database to analyze their corresponding metabolic pathways. The results demonstrated that Se-TP markedly improved the level of BUN and CORT in CFS rats. A total of eight differential metabolites were detected in GC-MS analysis, which were benzoic acid, itaconic acid, glutaric acid, 4-acetamidobutyric acid, creatine, 2-hydroxy-3-isopropylbutanedioic acid, l-dopa, and 21-hydroxypregnenolone. These differential metabolites were entered into the MetPA database to search for the corresponding metabolic pathways and three related metabolic pathways were screened out. The first pathway was steroid hormone biosynthesis. The second was tyrosine metabolism, and the third was arginine-proline metabolism. The 21-hydroxypregnenolone level of rats in the CFS group markedly increased after the Se-TP administration. In conclusion, Se-TP treatments on CFS rats improved their condition. Its metabolic mechanism was closely related to that which regulates the steroid hormone biosynthesis. Full article
(This article belongs to the Special Issue Polysaccharides)
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Open AccessArticle Synthesis of Phosphated K-Carrageenan and Its Application for Flame-Retardant Waterborne Epoxy
Polymers 2018, 10(11), 1268; https://doi.org/10.3390/polym10111268 (registering DOI)
Received: 18 October 2018 / Revised: 10 November 2018 / Accepted: 12 November 2018 / Published: 15 November 2018
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Abstract
In this paper, phosphated K-carrageenan (P-KC) was obtained by reacting POCl3 with the renewable source K-carrageenan (KC). P-KC and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were added into waterborne epoxy (EP) to improve its flame retardancy. The structure of P-KC was studied comprehensively using Fourier transform
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In this paper, phosphated K-carrageenan (P-KC) was obtained by reacting POCl3 with the renewable source K-carrageenan (KC). P-KC and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were added into waterborne epoxy (EP) to improve its flame retardancy. The structure of P-KC was studied comprehensively using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), showing the successful synthesis of P-KC. The flame retardancy of the EP was evaluated by the cone calorimeter test. The results showed that different mass ratios of DOPO and P-KC affected the flame retardancy of EP. When the mass ratio of DOPO and P-KC was 2:1, total heat release (THR) and total smoke production (TSP) decreased by 48.7% and 37.4%, respectively. The microstructures of residue char were observed by FTIR and scanning electron microscopy (SEM), indicating that the flame-retardant waterborne epoxy (FR-EP) system held a more cohesive and denser char structure. The char inhibited the diffusion of heat and oxygen, which played a key role in the flame retardancy. Full article
(This article belongs to the Special Issue Multi-functional Polymer Composites and Structures)
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Open AccessReview Biosynthesis and Characteristics of Aromatic Polyhydroxyalkanoates
Polymers 2018, 10(11), 1267; https://doi.org/10.3390/polym10111267
Received: 17 October 2018 / Revised: 5 November 2018 / Accepted: 9 November 2018 / Published: 14 November 2018
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Abstract
Polyhydroxyalkanoates (PHAs) are polyesters synthesized by bacteria as a carbon and energy storage material. PHAs are characterized by thermoplasticity, biodegradability, and biocompatibility, and thus have attracted considerable attention for use in medical, agricultural, and marine applications. The properties of PHAs depend on the
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Polyhydroxyalkanoates (PHAs) are polyesters synthesized by bacteria as a carbon and energy storage material. PHAs are characterized by thermoplasticity, biodegradability, and biocompatibility, and thus have attracted considerable attention for use in medical, agricultural, and marine applications. The properties of PHAs depend on the monomer composition and many types of PHA monomers have been reported. This review focuses on biosynthesized PHAs bearing aromatic groups as side chains. Aromatic PHAs show characteristics different from those of aliphatic PHAs. This review summarizes the types of aromatic PHAs and their characteristics, including their thermal and mechanical properties and degradation behavior. Furthermore, the effect of the introduction of an aromatic monomer on the glass transition temperature (Tg) of PHAs is discussed. The introduction of aromatic monomers into PHA chains is a promising method for improving the properties of PHAs, as the characteristics of aromatic PHAs differ from those of aliphatic PHAs. Full article
(This article belongs to the Special Issue Aromatic Polymers)
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Open AccessArticle Enzymatic Degradation of Star Poly(ε-Caprolactone) with Different Central Units
Polymers 2018, 10(11), 1266; https://doi.org/10.3390/polym10111266
Received: 19 October 2018 / Revised: 9 November 2018 / Accepted: 11 November 2018 / Published: 14 November 2018
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Abstract
Four-arm star poly(ε-caprolactone) with a central poly(ethylene glycol) PEG unit bridged with 2,2-bis(methyl) propionic acid, (PCL)2-b-PEG-b-(PCL)2, and six-arm star PCL homopolymer with a central dipentaerythritol units were hydrolysed using a lipase from Pseudomonas
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Four-arm star poly(ε-caprolactone) with a central poly(ethylene glycol) PEG unit bridged with 2,2-bis(methyl) propionic acid, (PCL)2-b-PEG-b-(PCL)2, and six-arm star PCL homopolymer with a central dipentaerythritol units were hydrolysed using a lipase from Pseudomonas cepacia and the Thermobifida cellulosilytica cutinase Thc_Cut1. For comparative analysis, Y-shaped copolymers containing methylated PEG bridged with bisMPA, MePEG-(PCL)2, and linear triblock copolymers PCL-b-PEG-b-PCL were also subjected to enzymatic hydrolysis. The hydrophilic nature of the polymers was determined using contact angle analysis, showing that a higher PEG content exhibited a lower contact angle and higher surface wettability. Enzymatic hydrolysis was monitored by % mass loss, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). A higher rate of mass loss was found for lipase catalysed hydrolysis of those polymers with the highest PEG content, leading to significant surface erosion and increase in crystallinity within the first two days. Liquid chromatography (LC) and size exclusion chromatography (SEC) of samples incubated with the cutinase showed a significant decrease in molecular weight, increase in dispersity, and release of ε-CL monomer units after 6 h of incubation. Full article
(This article belongs to the Special Issue Biocatalytic Functionalization and Degradation of Synthetic Polymers)
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Open AccessArticle Synergistic Effects of Bitumen Plasticization and Microwave Treatment on Short-Term Devulcanization of Ground Tire Rubber
Polymers 2018, 10(11), 1265; https://doi.org/10.3390/polym10111265
Received: 28 September 2018 / Revised: 9 November 2018 / Accepted: 11 November 2018 / Published: 13 November 2018
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Abstract
Ground tire rubber (GTR) was mechano-chemically modified with road bitumen 160/220 and subsequently treated using a microwave radiation. The combined impact of bitumen 160/220 content and microwave treatment on short-term devulcanization of GTR was studied by thermal camera, wavelength dispersive X-ray fluorescence spectrometry
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Ground tire rubber (GTR) was mechano-chemically modified with road bitumen 160/220 and subsequently treated using a microwave radiation. The combined impact of bitumen 160/220 content and microwave treatment on short-term devulcanization of GTR was studied by thermal camera, wavelength dispersive X-ray fluorescence spectrometry (WD-XRF), static headspace, and gas chromatography-mass spectrometry (SHS-GC-MS), thermogravimetric analysis combined with Fourier transform infrared spectroscopy (TGA-FTIR), oscillating disc rheometer and static mechanical properties measurements. The obtained results showed that bitumen plasticizer prevents oxidation of GTR during microwave treatment and simultaneously improves processing and thermal stability of obtained reclaimed rubber. Full article
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Open AccessArticle Preparation and Properties of SBS-g-GOs-Modified Asphalt Based on a Thiol-ene Click Reaction in a Bituminous Environment
Polymers 2018, 10(11), 1264; https://doi.org/10.3390/polym10111264
Received: 18 September 2018 / Revised: 5 November 2018 / Accepted: 6 November 2018 / Published: 13 November 2018
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Abstract
Styrene-butadiene styrene graphene oxide nanoplatelets (SBS-g-GOs)-modified asphalt was prepared by reacting thiolated GOs (GOs-SH) with SBS in asphalt using a thiol-ene click reaction. The temperature resistance and mechanical properties of asphalts were analyzed by dynamic shear rheology (DSR) and multiple-stress creep-recovery (MSCR) tests,
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Styrene-butadiene styrene graphene oxide nanoplatelets (SBS-g-GOs)-modified asphalt was prepared by reacting thiolated GOs (GOs-SH) with SBS in asphalt using a thiol-ene click reaction. The temperature resistance and mechanical properties of asphalts were analyzed by dynamic shear rheology (DSR) and multiple-stress creep-recovery (MSCR) tests, which revealed that an optimum amount of GOs-SH (0.02%) can effectively improve the low temperature and anti-rutting performance of SBS asphalt. Segregation experiments showed that SBS-g-GOs possessed good stability and dispersion in base asphalt. Fluorescence microscopy results revealed that the addition of GOs-SH promoted the formation of SBS network structure. Textural and morphological characterization of GOs-SH and SBS were achieved by Fourier transform infra-red (FT-IR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), atomic-force microscopy (AFM), X-ray diffraction (XRD), and scanning electron microscopy (SEM), while surface chemical composition was tested by X-ray photoelectron spectroscopy (XPS). Based on textural characterization data, a suitable reaction mechanism was proposed that involved the preferential reaction between GOs-SH and 1,2 C=C of SBS. The currently designed GOs-SH incorporated asphalt via thiol-ene click reaction provides new ideas for the preparation of modified asphalt with enhanced mechanical properties for target-oriented applications. Full article
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Open AccessArticle Study of Physical and Degradation Properties of 3D-Printed Biodegradable, Photocurable Copolymers, PGSA-co-PEGDA and PGSA-co-PCLDA
Polymers 2018, 10(11), 1263; https://doi.org/10.3390/polym10111263
Received: 15 October 2018 / Revised: 5 November 2018 / Accepted: 9 November 2018 / Published: 13 November 2018
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Abstract
As acrylated polymers become more widely used in additive manufacturing, their potential applications toward biomedicine also raise the demand for biodegradable, photocurable polymeric materials. Polycaprolactone diacrylate (PCLDA) and poly(ethylene glycol) diacrylate (PEGDA) are two popular choices of materials for stereolithography (SLA) and digital
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As acrylated polymers become more widely used in additive manufacturing, their potential applications toward biomedicine also raise the demand for biodegradable, photocurable polymeric materials. Polycaprolactone diacrylate (PCLDA) and poly(ethylene glycol) diacrylate (PEGDA) are two popular choices of materials for stereolithography (SLA) and digital light processing additive manufacturing (DLP-AM), and have been applied to many biomedical related research. However, both materials are known to degrade at a relatively low rate in vivo, limiting their applications in biomedical engineering. In this work, biodegradable, photocurable copolymers are introduced by copolymerizing PCLDA and/or PEGDA with poly(glycerol sebacate) acrylate (PGSA) to form a network polymer. Two main factors are discussed: the effect of degree of acrylation in PGSA and the weight ratio between the prepolymers toward the mechanical and degradation properties. It is found that by blending prepolymers with various degree of acrylation and at various weight ratios, the viscosity of the prepolymers remains stable, and are even more 3D printable than pure substances. The formation of various copolymers yielded a database with selectable Young’s moduli between 0.67–10.54 MPa, and the overall degradation rate was significantly higher than pure substance. In addition, it is shown that copolymers fabricated by DLP-AM fabrication presents higher mechanical strength than those fabricated via direct UV exposure. With the tunable mechanical and degradation properties, the photocurable, biodegradable copolymers are expected to enable a wider application of additive manufacturing toward tissue engineering. Full article
(This article belongs to the Special Issue Smart Polymers)
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Open AccessArticle Additive Manufactured Sandwich Composite/ABS Parts for Unmanned Aerial Vehicle Applications
Polymers 2018, 10(11), 1262; https://doi.org/10.3390/polym10111262
Received: 12 October 2018 / Revised: 27 October 2018 / Accepted: 3 November 2018 / Published: 13 November 2018
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Abstract
Fused deposition modelling (FDM) is one of most popular 3D printing techniques of thermoplastic polymers. Nonetheless, the poor mechanical strength of FDM parts restricts the use of this technology in functional parts of many applications such as unmanned aerial vehicles (UAVs) where lightweight,
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Fused deposition modelling (FDM) is one of most popular 3D printing techniques of thermoplastic polymers. Nonetheless, the poor mechanical strength of FDM parts restricts the use of this technology in functional parts of many applications such as unmanned aerial vehicles (UAVs) where lightweight, high strength, and stiffness are required. In the present paper, the fabrication process of low-density acrylonitrile butadiene styrenecarbon (ABS) with carbon fibre reinforced polymer (CFRP) sandwich layers for UAV structure is proposed to improve the poor mechanical strength and elastic modulus of printed ABS. The composite sandwich structures retains FDM advantages for rapid making of complex geometries, while only requires simple post-processing steps to improve the mechanical properties. Artificial neural network (ANN) was used to investigate the influence of the core density and number of CFRP layers on the mechanical properties. The results showed an improvement of specific strength and elastic modulus with increasing the number of CFRP. The specific strength of the samples improved from 20 to 145 KN·m/kg while the Young’s modulus increased from 0.63 to 10.1 GPa when laminating the samples with CFRP layers. On the other hand, the core density had no significant effect on both specific strength and elastic modulus. A case study was undertaken by applying the CFRP/ABS/CFRP sandwich structure using the proposed method to manufacture improved dual-tilting clamps of a quadcopter UAV. Full article
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Open AccessArticle Self-Structuring in Water of Polyamidoamino Acids with Hydrophobic Side Chains Deriving from Natural α-Amino Acids
Polymers 2018, 10(11), 1261; https://doi.org/10.3390/polym10111261
Received: 8 October 2018 / Revised: 31 October 2018 / Accepted: 11 November 2018 / Published: 13 November 2018
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Abstract
This paper reports on synthesis, acid-base properties and self-structuring in water of chiral polyamidoamino acids (PAACs) obtained by polyaddition of N,N′-methylenebisacrylamide with l-alanine, l-valine and l-leucine (M-l-Ala, M-l-Val, M-l-Leu) with potential
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This paper reports on synthesis, acid-base properties and self-structuring in water of chiral polyamidoamino acids (PAACs) obtained by polyaddition of N,N′-methylenebisacrylamide with l-alanine, l-valine and l-leucine (M-l-Ala, M-l-Val, M-l-Leu) with potential for selective interactions with biomolecules. The polymers maintained the acid-base properties of amino acids. In water, the circular dichroism spectra of PAACs revealed pH-dependent structuring in the range 3–11 and in the wavelength interval 200–280 nm. Taking as reference the values at pH 3, the differential molar ellipticities were plotted in the pH interval 3–11. Sigmoidal curves were obtained presenting inflection points at pH 8.1, 6.8 and 7.3 for M-l-Ala, M-l-Val and M-l-Leu, respectively, corresponding to the amine half-ionization. Theoretical modeling showed that PAACs assumed stable folded conformations. Intramolecular interactions led to transoid arrangements of the main chain reminiscent of protein hairpin motif. Oligomers with ten repeat units had simulated gyration radii consistent with the hydrodynamic radii obtained by dynamic light scattering. Full article
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Open AccessArticle Starch-Based Flexible Coating for Food Packaging Paper with Exceptional Hydrophobicity and Antimicrobial Activity
Polymers 2018, 10(11), 1260; https://doi.org/10.3390/polym10111260
Received: 31 October 2018 / Revised: 10 November 2018 / Accepted: 10 November 2018 / Published: 13 November 2018
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Abstract
Herein, we fabricated a starch-based flexible coating for food packaging papers with excellent hydrophobicity and antimicrobial properties. FTIR (Fourier transform infrared) and XRD (X-ray diffraction) spectra revealed the homogeneous dispersion of the ZnO nanoparticles (NPs) in the composite film within 5% ZnO NP
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Herein, we fabricated a starch-based flexible coating for food packaging papers with excellent hydrophobicity and antimicrobial properties. FTIR (Fourier transform infrared) and XRD (X-ray diffraction) spectra revealed the homogeneous dispersion of the ZnO nanoparticles (NPs) in the composite film within 5% ZnO NP dosage. SEM (scanning electron microscope) and AFM (atomic force microscope) micrographs confirmed the increased roughness on the composite film with the increased dosages of ZnO NPs. Hydrophobic characteristics showed that dramatic enhancement was obtained in the values and stabilities of DCAs (dynamic contact angles) in the resultant film and coated paper. TG (thermogravimetry) results demonstrated the increased thermal stabilities of the composite films. Significantly, a decreased water vapor transmission rate was observed in the coated paper. When 20% guanidine-based starch and 2% CMC (carboxy methyl cellulose) was added, a flexible coating with excellent antimicrobial activity towards Escherichia coli can be obtained. Furthermore, the migration of ZnO NPs into the food simulants was well below the overall migration legislative limit. The resultant starch-based flexible composite film and coated paper established an effective approach to develop a green-based material for food packaging applications. Full article
(This article belongs to the Special Issue Antimicrobial Polymers II)
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Open AccessArticle Novel Multifunctional Luminescent Electrospun Fluorescent Nanofiber Chemosensor-Filters and Their Versatile Sensing of pH, Temperature, and Metal Ions
Polymers 2018, 10(11), 1259; https://doi.org/10.3390/polym10111259
Received: 20 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 13 November 2018
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Abstract
Novel multifunctional fluorescent chemosensors composed of electrospun (ES) nanofibers with high sensitivity toward pH, mercury ions (Hg2+), and temperature were prepared from poly(N-Isopropylacrylamide-co-N-methylolacrylamide-co-rhodamine derivative) (poly(NIPAAm-co-NMA-co-RhBN2AM)) by employing an electrospinning
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Novel multifunctional fluorescent chemosensors composed of electrospun (ES) nanofibers with high sensitivity toward pH, mercury ions (Hg2+), and temperature were prepared from poly(N-Isopropylacrylamide-co-N-methylolacrylamide-co-rhodamine derivative) (poly(NIPAAm-co-NMA-co-RhBN2AM)) by employing an electrospinning process. NIPAAm and NMA moieties provide hydrophilic and thermo-responsive properties (absorption of Hg2+ in aqueous solutions), and chemical cross-linking sites (stabilization of the fibrous structure in aqueous solutions), respectively. The fluorescent probe, RhBN2AM is highly sensitive toward pH and Hg2+. The synthesis of poly(NIPAAm-co-NMA-co-RhBN2AM) with different compositions was carried on via free-radical polymerization. ES nanofibers prepared from sensory copolymers with a 71.1:28.4:0.5 NIPAAm:NMA:RhBN2AM ratio (P3 ES nanofibers) exhibited significant color change from non-fluorescent to red fluorescence while sensing pH (the λPL, max exhibited a 4.8-fold enhancement) or Hg2+ (at a constant Hg2+ concentration (10−3 M), the λPL, max of P3-fibers exhibited 4.7-fold enhancement), and high reversibility of on/off switchable fluorescence emission at least five times when Hg2+ and ethylenediaminetetraacetic acid (EDTA) were sequentially added. The P3 ES nanofibrous membranes had a higher surface-to-volume ratio to enhance their performance than did the corresponding thin films. In addition, the fluorescence emission of P3 ES nanofibrous membranes exhibited second enhancement above the lower critical solution temperature. Thus, the ES nanofibrous membranes prepared from P3 with on/off switchable capacity and thermo-responsive characteristics can be used as a multifunctional sensory device for specific heavy transition metal (HTM) in aqueous solutions. Full article
(This article belongs to the Special Issue Polymers for Chemosensing II)
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Open AccessArticle Synergistic Effect of Halloysite Nanotubes and Glycerol on the Physical Properties of Fish Gelatin Films
Polymers 2018, 10(11), 1258; https://doi.org/10.3390/polym10111258
Received: 3 October 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 13 November 2018
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Abstract
Fish gelatin (FG)/glycerol (GE)/halloysite (HT) composite films were prepared by casting method. The morphology of the composite films was observed by scanning electron microscopy (SEM). The effects of HT and GE addition on the mechanical properties, water resistance and optical properties of the
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Fish gelatin (FG)/glycerol (GE)/halloysite (HT) composite films were prepared by casting method. The morphology of the composite films was observed by scanning electron microscopy (SEM). The effects of HT and GE addition on the mechanical properties, water resistance and optical properties of the composites were investigated. Results showed that with increasing GE content, the elongation at composite breaks increased significantly, but their tensile strength (TS) and water resistance decreased. SEM results showed that GE can partly promote HT dispersion in composites. TS and water resistance also increased with the addition of HTs. Well-dispersed HTs in the FG matrix decreased the moisture uptake and water solubility of the composites. All films showed a transparency higher than 80% across the visible light region (400–800 nm), thereby indicating that light transmittance of the resulting nanocomposites was slightly affected by GE and HTs. Full article
(This article belongs to the Special Issue Polymer Clay Nano-composites)
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Open AccessArticle Biocompatibility of Poly(acrylonitrile-butadiene-styrene) Nanocomposites Modified with Silver Nanoparticles
Polymers 2018, 10(11), 1257; https://doi.org/10.3390/polym10111257
Received: 18 October 2018 / Revised: 6 November 2018 / Accepted: 11 November 2018 / Published: 13 November 2018
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Abstract
We evaluated the biological, mechanical, and surface properties of polymer nanocomposites manufactured via plastics processing, extrusion, and injection moulding. The aim of this study was to identify the interaction of fibroblasts and osteoblasts with materials intended for middle ear implants. We examined if
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We evaluated the biological, mechanical, and surface properties of polymer nanocomposites manufactured via plastics processing, extrusion, and injection moulding. The aim of this study was to identify the interaction of fibroblasts and osteoblasts with materials intended for middle ear implants. We examined if silver nanoparticles (AgNPs) may change the mechanical parameters of the polymer nanocomposites. In our study, the biostable polymer of thermoplastic acrylonitrile-butadiene-styrene (ABS) copolymer was used. Silver nanoparticles were applied as a modifier. We discuss surface parameters of the materials, including wettability and roughness, and evaluated the microstructure. The mechanical parameters, such as the Young’s modulus and tensile strength, were measured. Cytotoxicity tests were conducted on two cell lines: Hs680.Tr human fibroblasts and Saos-2 human osteoblasts. Cell viability, proliferation, and morphology in direct contact with nanocomposites were tested. Based on the results, the incorporated modifier was found to affect neither the number of osteoblasts nor the fibroblast cells. However, the addition of AgNPs had a relatively small effect on the cytotoxicity of the materials. A slight increase in the cytotoxicity of the test materials was observed with respect to the control, with the cytotoxicity of the materials tending to decrease after seven days for osteoblast cells, whereas it remained steady for fibroblasts. Based on optical microscope observation, the shape and morphology of the adhered cells were evaluated. After seven days of culture, fibroblasts and osteoblasts were properly shaped and evenly settled on the surface of both the pure polymer and the silver nanoparticle-modified composite. Water droplet tests demonstrated increased hydrophilicity when adding the AgNPs to ABS matrices, whereas roughness tests did not show changes in the surface topography of the investigated samples. The 0.5% by weight incorporation of AgNPs into ABS matrices did not influence the mechanical properties. Full article
(This article belongs to the Special Issue Antimicrobial Polymers II)
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Open AccessArticle Effect of Different Compatibilizers on Sustainable Composites Based on a PHBV/PBAT Matrix Filled with Coffee Silverskin
Polymers 2018, 10(11), 1256; https://doi.org/10.3390/polym10111256
Received: 13 October 2018 / Revised: 2 November 2018 / Accepted: 8 November 2018 / Published: 12 November 2018
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Abstract
This work investigates the feasibility of using coffee silverskin (CSS), one of the most abundant coffee waste products, as a reinforcing agent in biopolymer-based composites. The effect of using two compatibilizers, a maleinized linseed oil (MLO) and a traditional silane (APTES, (3-aminopropyl)triethoxysilane), on
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This work investigates the feasibility of using coffee silverskin (CSS), one of the most abundant coffee waste products, as a reinforcing agent in biopolymer-based composites. The effect of using two compatibilizers, a maleinized linseed oil (MLO) and a traditional silane (APTES, (3-aminopropyl)triethoxysilane), on mechanical and thermal behavior of sustainable composites based on a poly(butylene adipate-co-terephthalate/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PBAT/PHBV blend filled with coffee silverskin, in both the as-received state and after the extraction of antioxidants, was studied. Thermal (by differential scanning calorimetry), mechanical (by tensile testing), and morphological properties (by scanning electron microscopy) of injection molded biocomposites at three different weight contents (10, 20, and 30 wt %) were considered and discussed as a function of compatibilizer type. The effects of extraction procedure and silane treatment on surface properties of CSS were investigated by infrared spectroscopy. Obtained results confirmed that extracted CSS and silane-treated CSS provided the best combination of resistance properties and ductility, while MLO provided a limited compatibilization effect with CSS, due to the reduced amount of hydroxyl groups on CSS after extraction, suggesting that the effects of silane modification were more significant than the introduction of plasticizing agent. Full article
(This article belongs to the Special Issue Modification of Natural Fibres to Improve Biocomposites Performances)
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Open AccessArticle Synthesis, Characterization and Cytotoxicity of Novel Thermoresponsive Star Copolymers of N,N′-Dimethylaminoethyl Methacrylate and Hydroxyl-Bearing Oligo(Ethylene Glycol) Methacrylate
Polymers 2018, 10(11), 1255; https://doi.org/10.3390/polym10111255
Received: 19 October 2018 / Revised: 7 November 2018 / Accepted: 7 November 2018 / Published: 12 November 2018
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Abstract
Novel, nontoxic star copolymers of N,N-dimethylaminoethyl methacrylate (DMAEMA) and hydroxyl-bearing oligo(ethylene glycol) methacrylate (OEGMA-OH) were synthesized via atom transfer radical polymerization (ATRP) using hyperbranched poly(arylene oxindole) as the macroinitiator. Stars with molar masses from 100,000 g/mol to 257,000 g/mol and
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Novel, nontoxic star copolymers of N,N-dimethylaminoethyl methacrylate (DMAEMA) and hydroxyl-bearing oligo(ethylene glycol) methacrylate (OEGMA-OH) were synthesized via atom transfer radical polymerization (ATRP) using hyperbranched poly(arylene oxindole) as the macroinitiator. Stars with molar masses from 100,000 g/mol to 257,000 g/mol and with various amounts of OEGMA-OH in the arms were prepared. As these polymers can find applications, e.g., as carriers of nucleic acids, drugs or antibacterial or antifouling agents, in this work, much attention has been devoted to exploring their solution behavior and their stimuli-responsive properties. The behavior of the stars was studied in aqueous solutions under various pH and temperature conditions, as well as in PBS buffer, in Dulbecco’s modified Eagle’s medium (DMEM) and in organic solvents for comparison. The results indicated that increasing the content of hydrophilic OEGMA-OH units in the arms up to 10 mol% increased the cloud point temperature. For the stars with an OEGMA-OH content of 10 mol%, the thermo- and pH-responsivity was switched off. Since cytotoxicity experiments have shown that the obtained stars are less toxic than homopolymer DMAEMA stars, the presented studies confirmed that the prepared polymers are great candidates for the design of various nanosystems for biomedical applications. Full article
(This article belongs to the Special Issue Biocompatible Polymers)
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Open AccessArticle Reduced Graphene Oxide Embedded with MQ Silicone Resin Nano-Aggregates for Silicone Rubber Composites with Enhanced Thermal Conductivity and Mechanical Performance
Polymers 2018, 10(11), 1254; https://doi.org/10.3390/polym10111254
Received: 14 October 2018 / Revised: 6 November 2018 / Accepted: 6 November 2018 / Published: 12 November 2018
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Abstract
With developments of the electronics industry, more components are being included in electronic devices, which has led to challenges in thermal management. Using reduced graphene oxide embedded with MQ silicone resin (RGO/MQ) nano-aggregates as the composite filler and silicone rubber (SR) as the
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With developments of the electronics industry, more components are being included in electronic devices, which has led to challenges in thermal management. Using reduced graphene oxide embedded with MQ silicone resin (RGO/MQ) nano-aggregates as the composite filler and silicone rubber (SR) as the matrix, a simple approach is designed to prepare RGO/MQ/SR composites. Reduced graphene oxide (RGO) was first used as a substrate for the growth of MQ silicone resin by hybridization, forming sandwich-like micro structured RGO/MQ nano-aggregates successfully. Then, RGO/MQ was integrated into α,ω-dihydroxylpolydimethylsiloxane based on the in situ solvent-free blending method, followed by condensation and vulcanization, fabricating the final RGO/MQ/SR composites. The effective strategy could enhance the adaptability between graphene and silicone matrix under external stimuli at room temperature by embedding nanoscale MQ into the interface of graphene/silicone as the buffer layer. Obvious improvements were found in both thermal conductivity and mechanical properties due to excellent dispersion and interfacial compatibility of RGO/MQ in the host materials. These attractive results suggest that this RGO/MQ/SR composite has potential as a thermal interface material for heat dissipation applications. Full article
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Open AccessArticle A Novel Thin-Film Nanocomposite Nanofiltration Membrane by Incorporating 3D Hyperbranched Polymer Functionalized 2D Graphene Oxide
Polymers 2018, 10(11), 1253; https://doi.org/10.3390/polym10111253
Received: 22 October 2018 / Revised: 7 November 2018 / Accepted: 8 November 2018 / Published: 12 November 2018
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Abstract
In order to develop a high-performance thin-film nanocomposite (TFN) nanofiltration (NF) membrane, the functionalized graphene-based nanomaterial (GO-HBE-COOH) was synthesized by combining two-dimensional graphene oxide (GO) with a three-dimensional hyperbranched polymer, which was used as the novel nanofiller and successfully embedded into the polypiperazine-amide
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In order to develop a high-performance thin-film nanocomposite (TFN) nanofiltration (NF) membrane, the functionalized graphene-based nanomaterial (GO-HBE-COOH) was synthesized by combining two-dimensional graphene oxide (GO) with a three-dimensional hyperbranched polymer, which was used as the novel nanofiller and successfully embedded into the polypiperazine-amide (PPA) active layers on polysulfone (PSU) substrates via interfacial polymerization (IP) process. The resultant NF membranes were characterized using ATR-FTIR, SEM, and AFM, while their performance was evaluated in terms of water flux, salt rejection, antifouling ability, and chlorine resistance. The influence of GO-HBE-COOH concentration on the morphologies, properties, and performance of TFN NF membranes was investigated. With the addition of 60 ppm GO-HBE-COOH, the TFN-GHC-60 NF membrane exhibited the optimal water flux without a sacrifice of the salt rejection. It was found that the introduction of GO-HBE-COOH nanosheets favored the formation of a thinner and smoother nanocomposite active layer with an enhanced hydrophilicity and negative charge. As a result, TFN NF membranes demonstrated a superior permeaselectivity, antifouling ability, and chlorine resistance over the conventional PPA thin-film composite (TFC) membranes. Full article
(This article belongs to the Special Issue Polymer for Separation)
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Open AccessArticle The Effect of Substances of Plant Origin on the Thermal and Thermo-Oxidative Ageing of Aliphatic Polyesters (PLA, PHA)
Polymers 2018, 10(11), 1252; https://doi.org/10.3390/polym10111252
Received: 10 October 2018 / Revised: 1 November 2018 / Accepted: 7 November 2018 / Published: 12 November 2018
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Abstract
The stabilization efficiency of flavonoids (rutin and hesperidin) in polyester (polylactide (PLA) and polyhydroxyalkaonate (PHA)) composites under oxygen at high temperature was investigated. The polymer was homogenized with three antioxidants then processed by extrusion. The effects of stabilizers on the following physicochemical properties
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The stabilization efficiency of flavonoids (rutin and hesperidin) in polyester (polylactide (PLA) and polyhydroxyalkaonate (PHA)) composites under oxygen at high temperature was investigated. The polymer was homogenized with three antioxidants then processed by extrusion. The effects of stabilizers on the following physicochemical properties were investigated: melt flow, Vicat softening temperature, surface energy, and color change (Cie-Lab space). The aim of this study was to improve the stability of aliphatic polyesters by extending and controlling their lifetime. Differential Scanning Calorimetry DSC and Thermogravimetric analysis DTG methods were used to confirm the stabilizing effects (the inhibition of oxidation) of flavonoids (rutin and hesperidin) on the ageing process of biodegradable polymers. The levels of migration of plant antioxidants from PLA and PHA were determined and compared to the industrial stabilizer (Chimassorb 944 UV absorber). Based on this study, a comparable-to-higher efficiency of the proposed flavonoids for the stabilization of polyesters was found when compared to the commercial stabilizers. Thus, in the future, natural plant-derived substances may replace toxic hindered amines, which are commonly used as light stabilizers (HALS—Hindered Amine Light Stabilizers) in the polymer industry. Full article
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Open AccessArticle A Novel Eco-Friendly Wood Adhesive Composed by Sucrose and Ammonium Dihydrogen Phosphate
Polymers 2018, 10(11), 1251; https://doi.org/10.3390/polym10111251
Received: 4 October 2018 / Revised: 7 November 2018 / Accepted: 8 November 2018 / Published: 12 November 2018
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Abstract
Development of a bio-based wood adhesive is a significant goal for several wood-based material industries. In this study, a novel adhesive based upon sucrose and ammonium dihydrogen phosphate (ADP) was formulated in hopes of furthering this industrial goal through realization of a sustainable
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Development of a bio-based wood adhesive is a significant goal for several wood-based material industries. In this study, a novel adhesive based upon sucrose and ammonium dihydrogen phosphate (ADP) was formulated in hopes of furthering this industrial goal through realization of a sustainable adhesive with mechanical properties and water resistance comparable to the synthetic resins used today. Finished particleboards exhibited excellent mechanical properties and water resistance at the revealed optimal adhesive conditions. In fact, the board properties fulfilled in principle the requirements of JIS A 5908 18 type standard, however this occured at production conditions for the actual state of development as reported here, which are still different to usual industrial conditions. Thermal analysis revealed addition of ADP resulted in decreases to the thermal thresholds associated with degradation and curing of sucrose. Spectral results of FT-IR elucidated that furanic ring chemistry was involved during adhesive curing. A possible polycondensation reaction pathway was proposed from this data in an attempt to explain why the adhesive exhibited such favorable bonding properties. Full article
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Open AccessArticle Exploring Structure–Property Relationships in Aromatic Polybenzoxazines Through Molecular Simulation
Polymers 2018, 10(11), 1250; https://doi.org/10.3390/polym10111250
Received: 26 September 2018 / Revised: 31 October 2018 / Accepted: 7 November 2018 / Published: 12 November 2018
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Abstract
A series of commercial difunctional benzoxazine monomers are characterized using thermal and thermo-mechanical techniques before constructing representative polymer networks using molecular simulation techniques. Good agreement is obtained between replicate analyses and for the kinetic parameters obtained from differential scanning calorimetry data (and determined
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A series of commercial difunctional benzoxazine monomers are characterized using thermal and thermo-mechanical techniques before constructing representative polymer networks using molecular simulation techniques. Good agreement is obtained between replicate analyses and for the kinetic parameters obtained from differential scanning calorimetry data (and determined using the methods of Kissinger and Ozawa). Activation energies range from 85 to 108 kJ/mol (Kissinger) and 89 to 110 kJ/mol (Ozawa) for the uncatalyzed thermal polymerization reactions, which achieve conversions of between 85% and 97%. Glass transition temperatures determined from differential scanning calorimetry and dynamic mechanical thermal analysis are comparable, ranging from BA-a (151 °C, crosslink density 3.6 × 10−3 mol cm−3) containing the bisphenol A moiety to BP-a, based on a phenolphthalein bridge (239 to 256 °C, crosslink density 5.5 to 18.4 × 10−3 mol cm−3, depending on formulation). Molecular dynamics simulations of the polybenzoxazines generally agree well with empirical data, indicating that representative networks have been modelled. Full article
(This article belongs to the Special Issue Simulations of Polymers)
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Open AccessArticle Poly(3-hydroxybutyrate) Modified by Nanocellulose and Plasma Treatment for Packaging Applications
Polymers 2018, 10(11), 1249; https://doi.org/10.3390/polym10111249
Received: 24 October 2018 / Revised: 7 November 2018 / Accepted: 8 November 2018 / Published: 11 November 2018
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Abstract
In this work, a new eco-friendly method for the treatment of poly(3-hydroxybutyrate) (PHB) as a candidate for food packaging applications is proposed. Poly(3-hydroxybutyrate) was modified by bacterial cellulose nanofibers (BC) using a melt compounding technique and by plasma treatment or zinc oxide (ZnO)
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In this work, a new eco-friendly method for the treatment of poly(3-hydroxybutyrate) (PHB) as a candidate for food packaging applications is proposed. Poly(3-hydroxybutyrate) was modified by bacterial cellulose nanofibers (BC) using a melt compounding technique and by plasma treatment or zinc oxide (ZnO) nanoparticle plasma coating for better properties and antibacterial activity. Plasma treatment preserved the thermal stability, crystallinity and melting behavior of PHB‒BC nanocomposites, regardless of the amount of BC nanofibers. However, a remarkable increase of stiffness and strength and an increase of the antibacterial activity were noted. After the plasma treatment, the storage modulus of PHB having 2 wt % BC increases by 19% at room temperature and by 43% at 100 °C. The tensile strength increases as well by 21%. In addition, plasma treatment also inhibits the growth of Staphylococcus aureus and Escherichia coli by 44% and 63%, respectively. The ZnO plasma coating led to important changes in the thermal and mechanical behavior of PHB‒BC nanocomposite as well as in the surface structure and morphology. Strong chemical bonding of the metal nanoparticles on PHB surface following ZnO plasma coating was highlighted by infrared spectroscopy. Moreover, the presence of a continuous layer of self-aggregated ZnO nanoparticles was demonstrated by scanning electron microscopy, ZnO plasma treatment completely inhibiting growth of Staphylococcus aureus. A plasma-treated PHB‒BC nanocomposite is proposed as a green solution for the food packaging industry. Full article
(This article belongs to the Special Issue Antimicrobial Polymer-Based Materials for Food Packaging Applications)
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Open AccessReview Synthesis and Applications of Molecularly Imprinted Polymers Modified TiO2 Nanomaterials: A Review
Polymers 2018, 10(11), 1248; https://doi.org/10.3390/polym10111248
Received: 9 October 2018 / Revised: 2 November 2018 / Accepted: 8 November 2018 / Published: 11 November 2018
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Abstract
Titanium dioxide (TiO2) nanomaterials have caused a widespread concern in the past several decades for their bulk characteristics and potential applications in many different areas. Lately, the combination between molecularly imprinted polymers (MIPs) and TiO2 nanomaterials have been proven to
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Titanium dioxide (TiO2) nanomaterials have caused a widespread concern in the past several decades for their bulk characteristics and potential applications in many different areas. Lately, the combination between molecularly imprinted polymers (MIPs) and TiO2 nanomaterials have been proven to improve the relative adsorption capacity, selectivity and accelerate the rate of mass transfer of analyte which is not possible using TiO2 alone. Considering the unique performance of the MIPs modified TiO2 nanomaterials, this review intends to give an overview of the recent progresses in the development of MIPs modified TiO2 nanomaterials, the potential applications of their tailor-made characteristics. The limitations and challenges in this practically promising nanomaterials have also been raised and summarized. By means of the points raised in this article, we would like to provide some assistance for further development of preparation methodologies and the expansion of some potential applications in the field of MIPs modified TiO2 nanomaterials. Full article
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Open AccessArticle Facile, Scalable, Eco-Friendly Fabrication of High-Performance Flexible All-Solid-State Supercapacitors
Polymers 2018, 10(11), 1247; https://doi.org/10.3390/polym10111247
Received: 20 September 2018 / Revised: 5 November 2018 / Accepted: 8 November 2018 / Published: 11 November 2018
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Abstract
A highly porous freestanding supercapacitor electrode has been fabricated through a simple, inexpensive, bulk-scalable, and environmentally friendly method, without using any extra current collector, binder, or conducting additive. Benefiting from its unique micro-tubular hollow structure with a thin cell wall and large lumen,
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A highly porous freestanding supercapacitor electrode has been fabricated through a simple, inexpensive, bulk-scalable, and environmentally friendly method, without using any extra current collector, binder, or conducting additive. Benefiting from its unique micro-tubular hollow structure with a thin cell wall and large lumen, kapok fiber (KF) was used herein as a low-cost template for the successive growth of polypyrrole (PPy) through in situ chemical polymerization. This PPy-coated KF (KF@PPy) was blended with functionalized carbon nanotubes (f-CNTs) to form freestanding conductive films (KF@PPy/f-CNT) through a simple dispersion and filtration method. The hybrid film featuring the optimal composition exhibited an outstanding areal capacitance of 1289 mF cm−2 at a scan rate of 5 mV s−1. Moreover, an assembled all-solid-state symmetric supercapacitor featuring a PVA/H2SO4 gel electrolyte exhibited not only areal capacitances as high as 258 mF cm−2 (at a scan rate of 5 mV s−1) but also excellent cycling stability (97.4% of the initial capacitance after 2500 cycles). Therefore, this efficient, low-cost, scalable green synthesis strategy appears to be a facile and sustainable way of fabricating high-performance flexible supercapacitors incorporating a renewable cellulose material. Full article
(This article belongs to the Special Issue Smart Polymers)
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Open AccessArticle Bubble Melt Electrospinning for Production of Polymer Microfibers
Polymers 2018, 10(11), 1246; https://doi.org/10.3390/polym10111246
Received: 8 October 2018 / Revised: 4 November 2018 / Accepted: 7 November 2018 / Published: 10 November 2018
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Abstract
In this paper, we report an interesting bubble melt electrospinning (e-spinning) to produce polymer microfibers. Usually, melt e-spinning for fabricating ultrafine fibers needs “Taylor cone”, which is formed on the tip of the spinneret. The spinneret is also the bottleneck for mass production
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In this paper, we report an interesting bubble melt electrospinning (e-spinning) to produce polymer microfibers. Usually, melt e-spinning for fabricating ultrafine fibers needs “Taylor cone”, which is formed on the tip of the spinneret. The spinneret is also the bottleneck for mass production in melt e-spinning. In this work, a metal needle-free method was tried in the melt e-spinning process. The “Taylor cone” was formed on the surface of the broken polymer melt bubble, which was produced by an airflow. With the applied voltage ranging from 18 to 25 kV, the heating temperature was about 210–250 °C, and polyurethane (TPU) and polylactic acid (PLA) microfibers were successfully fabricated by this new melt e-spinning technique. During the melt e-spinning process, polymer melt jets ejected from the burst bubbles could be observed with a high-speed camera. Then, polymer microfibers could be obtained on the grounded collector. The fiber diameter ranged from 45 down to 5 μm. The results indicate that bubble melt e-spinning may be a promising method for needleless production in melt e-spinning. Full article
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Open AccessArticle Structural Ordering in SWCNT-Polyimide Nanocomposites and Its Influence on Their Mechanical Properties
Polymers 2018, 10(11), 1245; https://doi.org/10.3390/polym10111245
Received: 23 October 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 10 November 2018
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Abstract
Using fully-atomistic models, tens-microseconds-long molecular-dynamic modelling was carried out for the first time to simulate the kinetics of polyimides ordering induced by the presence of single-walled carbon nanotube (SWCNT) nanofillers. Three polyimides (PI) were considered with different dianhydride fragments, namely 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA),
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Using fully-atomistic models, tens-microseconds-long molecular-dynamic modelling was carried out for the first time to simulate the kinetics of polyimides ordering induced by the presence of single-walled carbon nanotube (SWCNT) nanofillers. Three polyimides (PI) were considered with different dianhydride fragments, namely 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (aBPDA), and 3,3′,4,4′-oxidiphthalic dianhydride (ODPA) and same diamine 1,4-bis[4-(4-aminophenoxy)phenoxy]benzene (diamine P3). Both crystallizable PI BPDA-P3 and two amorphous polyimides ODPA-P3 and aBPDA-P3 reinforced by SWCNTs were studied. The structural properties of the nanocomposites at temperature close to the bulk polymer melting point were studied. The mechanical properties were determined for the nanocomposites cooled down to the glassy state. It was found that the SWCNT nanofiller initiates’ structural ordering not only in the crystallizable BPDA-P3 but also in the amorphous ODPA-P3 samples were in agreement with previously obtained experimental results. Two stages of the structural ordering were detected in the presence of SWCNTs, namely the orientation of the planar moieties followed by the elongation of whole polymer chains. The first type of local ordering was observed on the microsecond time scale and did not lead to the change of the mechanical properties of a polymer binder in considered nanocomposites. At the end of the second stage, both BPDA-P3 and ODPA-P3 PI chains extended completely along the SWCNT surface, which in turn led to enhanced mechanical characteristics in their glassy state. Full article
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Open AccessArticle Cell Uptake and Biocompatibility of Nanoparticles Prepared from Poly(benzyl malate) (Co)polymers Obtained through Chemical and Enzymatic Polymerization in Human HepaRG Cells and Primary Macrophages
Polymers 2018, 10(11), 1244; https://doi.org/10.3390/polym10111244
Received: 16 October 2018 / Revised: 5 November 2018 / Accepted: 5 November 2018 / Published: 10 November 2018
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Abstract
The design of drug-loaded nanoparticles (NPs) appears to be a suitable strategy for the prolonged plasma concentration of therapeutic payloads, higher bioavailability, and the reduction of side effects compared with classical chemotherapies. In most cases, NPs are prepared from (co)polymers obtained through chemical
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The design of drug-loaded nanoparticles (NPs) appears to be a suitable strategy for the prolonged plasma concentration of therapeutic payloads, higher bioavailability, and the reduction of side effects compared with classical chemotherapies. In most cases, NPs are prepared from (co)polymers obtained through chemical polymerization. However, procedures have been developed to synthesize some polymers via enzymatic polymerization in the absence of chemical initiators. The aim of this work was to compare the acute in vitro cytotoxicities and cell uptake of NPs prepared from poly(benzyl malate) (PMLABe) synthesized by chemical and enzymatic polymerization. Herein, we report the synthesis and characterization of eight PMLABe-based polymers. Corresponding NPs were produced, their cytotoxicity was studied in hepatoma HepaRG cells, and their uptake by primary macrophages and HepaRG cells was measured. In vitro cell viability evidenced a mild toxicity of the NPs only at high concentrations/densities of NPs in culture media. These data did not evidence a higher biocompatibility of the NPs prepared from enzymatic polymerization, and further demonstrated that chemical polymerization and the nanoprecipitation procedure led to biocompatible PMLABe-based NPs. In contrast, NPs produced from enzymatically synthesized polymers were more efficiently internalized than NPs produced from chemically synthesized polymers. The efficient uptake, combined with low cytotoxicity, indicate that PMLABe-based NPs are suitable nanovectors for drug delivery, deserving further evaluation in vivo to target either hepatocytes or resident liver macrophages. Full article
(This article belongs to the Special Issue Biocompatible Polymers)
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Open AccessArticle Actuation Behavior of Multilayer Graphene Nanosheets/Polydimethylsiloxane Composite Films
Polymers 2018, 10(11), 1243; https://doi.org/10.3390/polym10111243
Received: 28 October 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 9 November 2018
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Abstract
The graphene nanosheets (GNS)/polydimethylsiloxane (PDMS) composite films with out-of-plane dielectric actuation behavior were prepared through a layer-by-layer spin coating process. The GNS-PDMS/PDMS composite films with 1~3 layers of GNS-PDMS films were spin coated on top of the PDMS film. The dielectric, mechanical, and
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The graphene nanosheets (GNS)/polydimethylsiloxane (PDMS) composite films with out-of-plane dielectric actuation behavior were prepared through a layer-by-layer spin coating process. The GNS-PDMS/PDMS composite films with 1~3 layers of GNS-PDMS films were spin coated on top of the PDMS film. The dielectric, mechanical, and electromechanical actuation properties of the composite films were investigated. The dielectric constant of the GNS-PDMS3/PDMS composite film at 1 kHz is 5.52, which is 1.7 times that of the GNS-PDMS1/PDMS composite film. The actuated displacement of the GNS-PDMS/PDMS composite films is greatly enhanced by increasing the number of GNS-PDMS layers. This study provides a novel alternative approach for fabricating high-performance actuators with out-of-plane actuation behavior. Full article
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