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Polymers, Volume 9, Issue 10 (October 2017)

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Open AccessArticle Effects of Covalent Functionalization of MWCNTs on the Thermal Properties and Non-Isothermal Crystallization Behaviors of PPS Composites
Polymers 2017, 9(10), 460; doi:10.3390/polym9100460
Received: 8 August 2017 / Revised: 10 September 2017 / Accepted: 15 September 2017 / Published: 21 September 2017
Cited by 1 | PDF Full-text (5624 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide) (PPS), as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs) via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can
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In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide) (PPS), as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs) via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can be seen from a Field-Emission Scanning Electron Microscope (FE-SEM) images. The thermal properties of the PPS/MWCNTs composites were characterized using a thermal conductivity analyzer, and a differential scanning calorimeter (DSC). To analyze the crystallization behavior of polymers under conditions similar with those in industry, the non-isothermal crystallization behaviors of the PPS/MWCNTs composites were confirmed using various kinetic equations, such as the modified Avrami equation and Avrami-Ozawa combined equation. The crystallization rate of PPS/1 wt % pristine MWCNTs composite (PPSP1) was faster because of the intrinsic nucleation effect of the MWCNTs. However, the crystallization rates of the composites containing covalently-functionalized MWCNTs were slower than PPSP1 because of the destruction of the MWCNTs graphitic structure via covalent functionalization. Furthermore, the activation energies calculated by Kissinger’s method were consistently decreased by covalent functionalization. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle Fabrication of Electrospun Polylactic Acid/Cinnamaldehyde/β-Cyclodextrin Fibers as an Antimicrobial Wound Dressing
Polymers 2017, 9(10), 464; doi:10.3390/polym9100464
Received: 7 August 2017 / Revised: 15 September 2017 / Accepted: 19 September 2017 / Published: 21 September 2017
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Abstract
Cinnamaldehyde (CA) was successfully encapsulated in β-cyclodextrin (β-CD), and polylactic acid (PLA)-based composite fibers were prepared by incorporating CA/β-CD via electrospinning. Morphological, structural, spectral, and antibacterial properties of different weight ratios of PLA:β-CD/CA (88:12, 94:6, 97:3, and 98.5:1.5) and PLA/CA/β-CD fibers were investigated.
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Cinnamaldehyde (CA) was successfully encapsulated in β-cyclodextrin (β-CD), and polylactic acid (PLA)-based composite fibers were prepared by incorporating CA/β-CD via electrospinning. Morphological, structural, spectral, and antibacterial properties of different weight ratios of PLA:β-CD/CA (88:12, 94:6, 97:3, and 98.5:1.5) and PLA/CA/β-CD fibers were investigated. PLA and CA/β-CD were incorporated by mixing of CA/β-CD inclusions to enhance the viscosity of the mixed solution. The mechanical properties and hydrophilicity of nanofibers were improved following the addition of CA/β-CD. Moreover, CA/β-CD improved the antibacterial activities of the mixture against Escherichia coli and Staphylococcus aureus. PLA/CA/β-CD-3 exhibited excellent antibacterial effects and low cytotoxicity. Thus, our study showed that PLA/CA/β-CD fibers may have applications as wound dressing materials and for use in other biomedical applications. Full article
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Open AccessArticle Shape Memory Polyurethanes Based on Zwitterionic Hard Segments
Polymers 2017, 9(10), 465; doi:10.3390/polym9100465
Received: 2 September 2017 / Revised: 17 September 2017 / Accepted: 18 September 2017 / Published: 21 September 2017
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Abstract
This work aimed at elucidating the influence of zwitterionic hard segments on the structures and properties of shape memory polyurethanes (SMPUs). A series of zwitterionic SMPUs was successfully prepared with N-methyldiethanolamine (MDEA), 1,3-propanesultone (1,3-PS), 1,6-hexamethylene diisocyanate (HDI) and polyethylene glycol (PEG6000). The
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This work aimed at elucidating the influence of zwitterionic hard segments on the structures and properties of shape memory polyurethanes (SMPUs). A series of zwitterionic SMPUs was successfully prepared with N-methyldiethanolamine (MDEA), 1,3-propanesultone (1,3-PS), 1,6-hexamethylene diisocyanate (HDI) and polyethylene glycol (PEG6000). The influence of MDEA-PS-based zwitterionic hard segment on structure, morphology, thermal property, shape memory property and cytocompatibility were systematically investigated. The results demonstrated that the PEG-based zwitterionic SMPUs (PEG-ZSMPUs) formed phase separation structure consisting of crystalline soft phase and amorphous hard phase. The MDEA-PS zwitterionic segments showed a tendency to form ionic clusters in hard segments, which served as reinforced net points. Shape memory analysis showed that zwitterionic PEG-ZSMPUs containing a high content of zwitterionic segments had thermal-induced shape memory effects. Finally, cytotoxic assays demonstrated that MDEA-PS zwitterionic segment improved the biocompatibility of PEG-ZSMPUs. The zwitterionic PEG-ZSMPUs could thus have a promising application in smart biomedical fields. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessArticle Surface Properties and Structural Transformation Behaviors of mPEG-Maleic Rosin Copolymer in Water
Polymers 2017, 9(10), 466; doi:10.3390/polym9100466
Received: 18 August 2017 / Revised: 12 September 2017 / Accepted: 15 September 2017 / Published: 21 September 2017
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Abstract
mPEG (monomethoxy poly(ethylene glycol))-maleic rosin copolymer was successfully prepared. The surface properties of the copolymer were investigated by surface tension and resonance scattering techniques. The critical micelle concentration (CMC) was obtained. The adsorption behaviors and the conformational changes of the surfactant molecules at
[...] Read more.
mPEG (monomethoxy poly(ethylene glycol))-maleic rosin copolymer was successfully prepared. The surface properties of the copolymer were investigated by surface tension and resonance scattering techniques. The critical micelle concentration (CMC) was obtained. The adsorption behaviors and the conformational changes of the surfactant molecules at the air-water interface were described. The adsorption amount of state 1 presented a sinusoid shape and that of state 2 presented a sigmoid with the growth of П. The free energy of adsorption is more negative than that of micellization, thus, the surfactant molecules adsorb on the surface firstly, and then form micelles after saturation adsorption. Accordingly, structural transformation and aggregation behaviors of various concentration mPEG-maleic rosin copolymers with changing temperature were explored in water. The mPEG-maleic rosin chains experienced transformation from unimers to aggregates, to contracted aggregates, to cohesive aggregates with increasing temperature when the concentration is lower than CMC. This process is almost reversible with decreasing temperature. Transformation from micelle to aggregate with increasing temperature happened when the concentration is higher than CMC. The phenomena were assessed by DLS (dynamic light scattering) and SEM (scanning electron microscopy) techniques. Full article
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Open AccessArticle Enhanced Performance of Nanoporous Titanium Dioxide Solar Cells Using Cadmium Sulfide and Poly(3-hexylthiophene) Co-Sensitizers
Polymers 2017, 9(10), 467; doi:10.3390/polym9100467
Received: 20 August 2017 / Revised: 15 September 2017 / Accepted: 19 September 2017 / Published: 22 September 2017
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Abstract
This work reports the effect of co-sensitization of nanoporous titanium dioxide using Cadmium Sulfide (CdS) and poly(3-hexylthiophene) (P3HT) on the performance of hybrid solar cells. CdS nanolayer with different thicknesses was grown on Titanium Dioxide (TiO2) nanoparticles by chemical bath deposition
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This work reports the effect of co-sensitization of nanoporous titanium dioxide using Cadmium Sulfide (CdS) and poly(3-hexylthiophene) (P3HT) on the performance of hybrid solar cells. CdS nanolayer with different thicknesses was grown on Titanium Dioxide (TiO2) nanoparticles by chemical bath deposition technique with varying deposition times. Both atomic force microscopy (AFM) and UV–Vis–NIR spectroscopy measurements of TiO2 electrode sensitized with and without CdS layer confirm that the existence of CdS layer on TiO2 nanoparticles. AFM images of CdS-coated TiO2 nanoparticles show that the surface roughness of the TiO2 nanoparticle samples decreases with increasing CdS deposition times. Current density–voltage and external quantum efficiency (EQE) measurements were carried out for corresponding solar cells. Both short circuit current density (JSC) and fill factor were optimized at the CdS deposition time of 12 min. On the other hand, a steady and continuous increment in the open circuit voltage (VOC) was observed with increasing CdS deposition time and increased up to 0.81 V when the deposition time was 24 min. This may be attributed to the increased gradual separation of P3HT and TiO2 phases and their isolation at the interfaces. The higher VOC of 0.81 V was due to the higher built-in voltage at the CdS–P3HT interface when compared to that at the TiO2–P3HT interface. Optimized nanoporous TiO2 solar cells with CdS and P3HT co-sensitizers showed external quantum efficiency (EQE) of over 40% and 80% at the wavelengths corresponding to strong absorption of the polymer and CdS, respectively. The cells showed an overall average efficiency of over 2.4% under the illumination of 70 mW/cm2 at AM 1.5 condition. Full article
(This article belongs to the Special Issue Polymer Solar Cells)
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Open AccessArticle pH-Mediated Antibacterial Dyeing of Cotton with Prodigiosins Nanomicelles Produced by Microbial Fermentation
Polymers 2017, 9(10), 468; doi:10.3390/polym9100468
Received: 19 August 2017 / Revised: 15 September 2017 / Accepted: 20 September 2017 / Published: 23 September 2017
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Abstract
This study developed a novel pH-mediated antimicrobial dyeing process of cotton with prodigiosins nanomicelles produced by microbial fermentation. The average diameter of the pigment nanomicelles was 223.8 nm (range of 92.4–510.2 nm), and the pigment concentration was 76.46 mg/L. It was found that
[...] Read more.
This study developed a novel pH-mediated antimicrobial dyeing process of cotton with prodigiosins nanomicelles produced by microbial fermentation. The average diameter of the pigment nanomicelles was 223.8 nm (range of 92.4–510.2 nm), and the pigment concentration was 76.46 mg/L. It was found that the superior dyeing effect of cotton fabric was achieved by adjusting the dye bath pH. When the pH was three, dyed cotton under 90 °C for 60 min exhibited the greatest color strength with good rubbing, washing and perspiration color fastness. By the breaking strength test and XRD analysis, it was concluded that the cotton dyed under the optimum condition almost suffered no damage. In addition, due to the presence of prodigiosins, dyed cotton fabric under the optimal process showed outstanding bacteriostatic rates of 99.2% and 85.5% against Staphylococcus aureus and Escherichia coli, respectively. This research provided an eco-friendly and widely-applicable approach for antimicrobial intracellular pigments with the property of pH-sensitive solubility in water to endow cellulose fabric with color and antibacterial activity. Full article
(This article belongs to the Special Issue Antimicrobial Polymers)
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Open AccessArticle Fabrication of Hypericin Imprinted Polymer Nanospheres via Thiol-Yne Click Reaction
Polymers 2017, 9(10), 469; doi:10.3390/polym9100469
Received: 31 August 2017 / Revised: 20 September 2017 / Accepted: 21 September 2017 / Published: 24 September 2017
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Abstract
To fabricate molecularly imprinted polymer nanospheres via click reaction, five different clickable compounds were synthesized and two types of click reactions (azide-alkyne and thiol-yne) were explored. It was found that molecularly imprinted polymer nanospheres could be successfully synthesized via thiol-yne click reaction using
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To fabricate molecularly imprinted polymer nanospheres via click reaction, five different clickable compounds were synthesized and two types of click reactions (azide-alkyne and thiol-yne) were explored. It was found that molecularly imprinted polymer nanospheres could be successfully synthesized via thiol-yne click reaction using 3,5-diethynyl-pyridine (1) as the monomer, tris(3-mercaptopropionate) (tri-thiol, 5) as the crosslinker, and hypericin as the template (MIP–NSHs). The click polymerization completed in merely 4 h to produce the desired MIP–NSHs, which were characterized by FTIR, SEM, DLS, and BET, respectively. The reaction conditions for adsorption capacity and selectivity towards hypericin were optimized, and the MIP–NSHs synthesized under the optimized conditions showed a high adsorption capacity (Q = 6.03 μmol•g−1) towards hypericin. The imprinting factors of MIP–NSHs towards hypericin, protohypericin, and emodin were 2.44, 2.88, and 2.10, respectively. Full article
(This article belongs to the Special Issue Polymers and Block Copolymers at Interfaces and Surfaces)
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Open AccessFeature PaperArticle Effects of Lateral and Terminal Chains of X-Shaped Bolapolyphiles with Oligo(phenylene ethynylene) Cores on Self-Assembly Behaviour. Part 1: Transition between Amphiphilic and Polyphilic Self-Assembly in the Bulk
Polymers 2017, 9(10), 471; doi:10.3390/polym9100471
Received: 29 August 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 26 September 2017
Cited by 1 | PDF Full-text (13767 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polyphilic self-assembly leads to compartmentalization of space and development of complex structures in soft matter on different length scales, reaching from the morphologies of block copolymers to the liquid crystalline (LC) phases of small molecules. Whereas block copolymers are known to form membranes
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Polyphilic self-assembly leads to compartmentalization of space and development of complex structures in soft matter on different length scales, reaching from the morphologies of block copolymers to the liquid crystalline (LC) phases of small molecules. Whereas block copolymers are known to form membranes and interact with phospholipid bilayers, liquid crystals have been less investigated in this respect. Here, series of bolapolyphilic X-shaped molecules were synthesized and investigated with respect to the effect of molecular structural parameters on the formation of LC phases (part 1), and on domain formation in phospholipid bilayer membranes (part 2). The investigated bolapolyphiles are based on a rod-like π-conjugated oligo(phenylene ethynylene) (OPE) core with two glycerol groups being either directly attached or separated by additional ethylene oxide (EO) units to both ends. The X-shape is provided by two lateral alkyl chains attached at opposite sides of the OPE core, being either linear, branched, or semiperfluorinated. In this report, the focus is on the transition from polyphilic (triphilic or tetraphilic) to binary amphiphilic self-assembly. Polyphilic self-assembly, i.e., segregation of all three or four incorporated units into separate nano-compartments, leads to the formation of hexagonal columnar LC phases, representing triangular honeycombs. A continuous transition from the well-defined triangular honeycomb structures to simple hexagonal columnar phases, dominated by the arrangement of polar columns on a hexagonal lattice in a mixed continuum formed by the lipophilic chains and the OPE rods, i.e., to amphiphilic self-assembly, was observed by reducing the length and volume of the lateral alkyl chains. A similar transition was found upon increasing the length of the EO units involved in the polar groups. If the lateral alkyl chains are enlarged or replaced by semiperfluorinated chains, then the segregation of lateral chains and rod-like cores is retained, even for enlarged polar groups, i.e., the transition from polyphilic to amphiphilic self-assembly is suppressed. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Imidazole, a New Tunable Reagent for Producing Nanocellulose, Part I: Xylan-Coated CNCs and CNFs
Polymers 2017, 9(10), 473; doi:10.3390/polym9100473
Received: 15 August 2017 / Revised: 15 September 2017 / Accepted: 22 September 2017 / Published: 27 September 2017
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Abstract
Imidazole is reported to be an effective reactant for the production of nanocellulose from hardwood pulp. The morphologies and surface properties of the nanocellulose can be simply tailored according to the water content in the imidazole system: with pure imidazole, cellulose nanofibrils (CNFs)
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Imidazole is reported to be an effective reactant for the production of nanocellulose from hardwood pulp. The morphologies and surface properties of the nanocellulose can be simply tailored according to the water content in the imidazole system: with pure imidazole, cellulose nanofibrils (CNFs) in a yield of 10 wt % can be produced. With 25 wt % of water in imidazole, cellulose nanocrystals (CNCs) are obtained in 20 wt % yield. Both nanocelluloses exhibit crystallinity indices in the order of 70%. Interestingly, they retain the original xylan from the pulp with ca. 9–10 wt % of residual xylan content. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Open AccessArticle Design of a Versatile pH-Responsive Hydrogel for Potential Oral Delivery of Gastric-Sensitive Bioactives
Polymers 2017, 9(10), 474; doi:10.3390/polym9100474
Received: 21 August 2017 / Revised: 25 September 2017 / Accepted: 25 September 2017 / Published: 27 September 2017
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Abstract
A pH-responsive hydrogel system was prepared by free radical polymerization of acrylamide and methyl acrylic acid in the presence of N-N′-methylene bisacrylamide. Sodium bicarbonate was further applied as a blowing agent, which afforded a porous hydrogel structure. The hydrogel system
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A pH-responsive hydrogel system was prepared by free radical polymerization of acrylamide and methyl acrylic acid in the presence of N-N′-methylene bisacrylamide. Sodium bicarbonate was further applied as a blowing agent, which afforded a porous hydrogel structure. The hydrogel system achieved a constant super swelling rate within simulated intestinal buffer (~4%/min) and remained relatively static within simulated gastric buffer (~0.8%/min). The hydrogel system was able to achieve matrix resilience greater than 30% under a relatively high strain of 40%. In addition, the hydrogel system demonstrated significant swelling properties in response to simulated intestinal environmental over 24 h, with contrasting characteristics in simulated gastric buffer. The hydrogel demonstrated type IV isotherm porosity characteristics, with remarkable MRI and SEM variations in gastric and intestinal simulated fluids. Drug loading was observed to be greater than 98% using theophylline as a prototype drug, evaluating its controlled release kinetics over 24 h. The hydrogel exhibited substantial pH-responsive activity, which could be used as a versatile platform for targeted release of gastric-sensitive therapeutics to the small intestine. Full article
(This article belongs to the Special Issue Stimuli Responsive Polymers)
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Open AccessArticle Synthesis of Polystyrene–Polyphenylsiloxane Janus Particles through Colloidal Assembly with Unexpected High Selectivity: Mechanistic Insights and Their Application in the Design of Polystyrene Particles with Multiple Polyphenylsiloxane Patches
Polymers 2017, 9(10), 475; doi:10.3390/polym9100475
Received: 1 September 2017 / Revised: 21 September 2017 / Accepted: 26 September 2017 / Published: 28 September 2017
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Abstract
Janus particles are of great research interest because of their reduced symmetry, which provides them with unique physical and chemical properties. Such particles can be prepared from spherical structures through colloidal assembly. Whilst colloidal assembly has the potential to be a low cost
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Janus particles are of great research interest because of their reduced symmetry, which provides them with unique physical and chemical properties. Such particles can be prepared from spherical structures through colloidal assembly. Whilst colloidal assembly has the potential to be a low cost and scalable process, it typically lacks selectivity. As a consequence, it results in a complex mixture of particles of different architectures, which is tedious to purify. Very recently, we reported the colloidal synthesis of Au semishells, making use of polystyrene–polyphenylsiloxane Janus particles as an intermediate product (Chem. Commun. 2017, 53, 3898–3901). Here, we demonstrate that these Janus particles are realized through colloidal assembly of spherical glucose-functionalized polystyrene particles and an emulsion of phenyltrimethoxysilane in aqueous ammonia, followed by interfacial polycondensation to form the polyphenylsiloxane patch. Both the polystyrene spheres and the emulsion of Ph-TMS in aqueous ammonia are stabilized by a surfmer—a reactive surfactant. The colloidal assembly reported in this manuscript proceeds with an unexpected high selectivity, which makes this process exceptionally interesting for the synthesis of Janus particles. Furthermore, we report insights into the details of the mechanism of formation of these Janus particles, and apply those to adapt the synthesis conditions to produce polystyrene particles selectively decorated with multiple polyphenylsiloxane patches, e.g., raspberry particles. Full article
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Open AccessFeature PaperArticle Effects of Lateral and Terminal Chains of X-Shaped Bolapolyphiles with Oligo(phenylene ethynylene) Cores on Self-Assembly Behavior. Part 2: Domain Formation by Self-Assembly in Lipid Bilayer Membranes
Polymers 2017, 9(10), 476; doi:10.3390/polym9100476
Received: 1 September 2017 / Revised: 20 September 2017 / Accepted: 22 September 2017 / Published: 29 September 2017
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Abstract
Supramolecular self-assembly of membrane constituents within a phospholipid bilayer creates complex functional platforms in biological cells that operate in intracellular signaling, trafficking and membrane remodeling. Synthetic polyphilic compounds of macromolecular or small size can be incorporated into artificial phospholipid bilayers. Featuring three or
[...] Read more.
Supramolecular self-assembly of membrane constituents within a phospholipid bilayer creates complex functional platforms in biological cells that operate in intracellular signaling, trafficking and membrane remodeling. Synthetic polyphilic compounds of macromolecular or small size can be incorporated into artificial phospholipid bilayers. Featuring three or four moieties of different philicities, they reach beyond ordinary amphiphilicity and open up avenues to new functions and interaction concepts. Here, we have incorporated a series of X-shaped bolapolyphiles into DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) bilayers of giant unilamellar vesicles. The bolapolyphiles consist of a rod-like oligo(phenylene ethynylene) (OPE) core, hydrophilic glycerol-based headgroups with or without oligo(ethylene oxide) expansions at both ends and two lateral alkyl chains attached near the center of the OPE core. In the absence of DPPC and water, the compounds showed thermotropic liquid-crystalline behavior with a transition between polyphilic and amphiphilic assembly (see part 1 in this issue). In DPPC membranes, various trends in the domain morphologies were observed upon structure variations, which entailed branched alkyl chains of various sizes, alkyl chain semiperfluorination and size expansion of the headgroups. Observed effects on domain morphology are interpreted in the context of the bulk behavior (part 1) and of a model that was previously developed based on spectroscopic and physicochemical data. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Supported Ionic Liquid Silica as Curing Agent for Epoxy Composites with Improved Mechanical and Thermal Properties
Polymers 2017, 9(10), 478; doi:10.3390/polym9100478
Received: 1 September 2017 / Revised: 28 September 2017 / Accepted: 28 September 2017 / Published: 29 September 2017
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Abstract
The present study aims to improve the mechanical properties of epoxy composite by incorporating supported ionic liquid silica (IL-silica). The IL-silica not only showed improved interfacial interaction and reinforcement, but also served as cure agent of epoxy composites. The differential scanning calorimetry analysis
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The present study aims to improve the mechanical properties of epoxy composite by incorporating supported ionic liquid silica (IL-silica). The IL-silica not only showed improved interfacial interaction and reinforcement, but also served as cure agent of epoxy composites. The differential scanning calorimetry analysis revealed that epoxy composites could be successfully cured with IL-silica without any routine curing agents. IL-silica/epoxy composites presented higher mechanical and thermal properties compared with epoxy composite containing un-functionalized silica (u-silica). The dynamic mechanical analysis showed that the storage modulus of composites significantly increased with the addition of IL-silica in comparison to that with added u-silica, as well as the variation of Tg parameter. The incorporation of IL-silica simultaneously enhanced the tensile strength, toughness, and thermal stability of the epoxy composites. The considerable improvements in mechanical and thermal properties are ascribed to the improved dispersion of IL-silica and the enhanced interfacial interactions between epoxy matrix and IL-silica by strong covalent bonding, which results in an effective load transfer. Full article
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Open AccessArticle Biocompatible Silk/Polymer Energy Harvesters Using Stretched Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) Nanofibers
Polymers 2017, 9(10), 479; doi:10.3390/polym9100479
Received: 28 August 2017 / Revised: 25 September 2017 / Accepted: 28 September 2017 / Published: 30 September 2017
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Abstract
Energy harvested from human body movement can produce continuous, stable energy to portable electronics and implanted medical devices. The energy harvesters need to be light, small, inexpensive, and highly portable. Here we report a novel biocompatible device made of poly (vinylidene fluoride-co
[...] Read more.
Energy harvested from human body movement can produce continuous, stable energy to portable electronics and implanted medical devices. The energy harvesters need to be light, small, inexpensive, and highly portable. Here we report a novel biocompatible device made of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers on flexible substrates. The nanofibers are prepared with electrospinning followed by a stretching process. This results in aligned nanofibers with diameter control. The assembled device demonstrates high mechanical-to-electrical conversion performance, with stretched PVDF-HFP nanofibers outperforming regular electrospun samples by more than 10 times. Fourier transform infrared spectroscopy (FTIR) reveals that the stretched nanofibers have a higher β phase content, which is the critical polymorph that enables piezoelectricity in polyvinylidene fluoride (PVDF). Polydimethylsiloxane (PDMS) is initially selected as the substrate material for its low cost, high flexibility, and rapid prototyping capability. Bombyx Mori silkworm silk fibroin (SF) and its composites are investigated as promising alternatives due to their high strength, toughness, and biocompatibility. A composite of silk with 20% glycerol demonstrates higher strength and larger ultimate strain than PDMS. With the integration of stretched electrospun PVDF-HFP nanofibers and flexible substrates, this pilot study shows a new pathway for the fabrication of biocompatible, skin-mountable energy devices. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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Open AccessArticle Effect of Aging, Antioxidant, and Mono- and Divalent Ions at High Temperature on the Rheology of New Polyacrylamide-Based Co-Polymers
Polymers 2017, 9(10), 480; doi:10.3390/polym9100480
Received: 31 July 2017 / Revised: 21 September 2017 / Accepted: 26 September 2017 / Published: 4 October 2017
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Abstract
The viscosity of four new polymers was investigated for the effect of aging at high temperature, with varying degrees of salinity and hardness. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; AN132 VHM; SUPERPUSHER SAV55; and THERMOASSOCIATIF copolymers. All polymer samples were
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The viscosity of four new polymers was investigated for the effect of aging at high temperature, with varying degrees of salinity and hardness. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; AN132 VHM; SUPERPUSHER SAV55; and THERMOASSOCIATIF copolymers. All polymer samples were aged at 80 °C for varying times (from zero to at least 90 days) with and without isobutyl alcohol (IBA) as an antioxidant. To see the effect of divalent ions on the polymer solution viscosity, parallel experiments were performed in a mixture of CaCl2-NaCl of the same ionic strength as 5 wt % NaCl. The polymers without IBA showed severe viscosity reduction after aging for 90 days in both types of preparation (5 wt % NaCl or CaCl2-NaCl). In the presence of IBA, viscosity was increased when aging time was increased for 5 wt % NaCl. In CaCl2-NaCl, on the other hand, a viscosity reduction was observed as aging time was increased. This behavior was observed for all polymers except AN132 VHM. Full article
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Open AccessArticle Polystyrene Chain Growth from Di-End-Functional Polyolefins for Polystyrene-Polyolefin-Polystyrene Block Copolymers
Polymers 2017, 9(10), 481; doi:10.3390/polym9100481
Received: 28 August 2017 / Revised: 19 September 2017 / Accepted: 29 September 2017 / Published: 2 October 2017
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Abstract
Triblock copolymers of polystyrene (PS) and a polyolefin (PO), e.g., PS-block-poly(ethylene-co-1-butene)-block-PS (SEBS), are attractive materials for use as thermoplastic elastomers and are produced commercially by a two-step process that involves the costly hydrogenation of PS-block-polybutadiene-
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Triblock copolymers of polystyrene (PS) and a polyolefin (PO), e.g., PS-block-poly(ethylene-co-1-butene)-block-PS (SEBS), are attractive materials for use as thermoplastic elastomers and are produced commercially by a two-step process that involves the costly hydrogenation of PS-block-polybutadiene-block-PS. We herein report a one-pot strategy for attaching PS chains to both ends of PO chains to construct PS-block-PO-block-PS directly from olefin and styrene monomers. Dialkylzinc compound containing styrene moieties ((CH2=CHC6H4CH2CH2)2Zn) was prepared, from which poly(ethylene-co-propylene) chains were grown via “coordinative chain transfer polymerization” using the pyridylaminohafnium catalyst to afford di-end functional PO chains functionalized with styrene and Zn moieties. Subsequently, PS chains were attached at both ends of the PO chains by introduction of styrene monomers in addition to the anionic initiator Me3SiCH2Li·(pmdeta) (pmdeta = pentamethyldiethylenetriamine). We found that the fraction of the extracted PS homopolymer was low (~20%) and that molecular weights were evidently increased after the styrene polymerization (ΔMn = 27–54 kDa). Transmission electron microscopy showed spherical and wormlike PS domains measuring several tens of nm segregated within the PO matrix. Optimal tensile properties were observed for the sample containing a propylene mole fraction of 0.25 and a styrene content of 33%. Finally, in the cyclic tensile test, the prepared copolymers exhibited thermoplastic elastomeric properties with no breakage up over 10 cycles, which is comparable to the behavior of commercial-grade SEBS. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessArticle QCM Biosensor Based on Polydopamine Surface for Real-Time Analysis of the Binding Kinetics of Protein-Protein Interactions
Polymers 2017, 9(10), 482; doi:10.3390/polym9100482
Received: 7 September 2017 / Revised: 28 September 2017 / Accepted: 29 September 2017 / Published: 2 October 2017
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Abstract
A quartz crystal microbalance (QCM) biosensor based on polydopamine (PDA) surface was developed for real-time analysis of the binding kinetics of protein-protein interactions. The biosensor was fabricated by simply immersing the gold sensor chip into an aqueous dopamine solution at pH 8.5 leading
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A quartz crystal microbalance (QCM) biosensor based on polydopamine (PDA) surface was developed for real-time analysis of the binding kinetics of protein-protein interactions. The biosensor was fabricated by simply immersing the gold sensor chip into an aqueous dopamine solution at pH 8.5 leading to a spontaneous deposition of PDA film onto the sensor chip surface, which was followed by incubation with the protein to immobilize it onto the PDA-coated sensor chip surface via Michael addition and/or Schiff base reactions. In this paper, the interaction between monoclonal anti-myoglobin 7005 antibody (IgG1) and its antigen human cardiac myoglobin was used as a model system for real-time analysis of biomolecule interactions on the biosensor surface. The kinetic parameters of the interaction between anti-myoglobin 7005 and myoglobin were studied on the biosensor surface, which were consistent with the results obtained via amine coupling. The biosensor based on PDA surface has excellent regenerability, reproducibility, and specificity. Compared with the most frequently/typically used amine coupling method for immobilization of proteins on carboxylated substrates, the modification methodology presented in this paper is simple, mild and is not subjected to the limitations of the isoelectric point (pI) of the protein. In addition, the PDA biosensor chip can be easily reused, which makes QCM biosensor analysis more efficient and cost effective. Full article
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Open AccessCommunication Vesicles in Multiple Shapes: Fine-Tuning Polymersomes’ Shape and Stability by Setting Membrane Hydrophobicity
Polymers 2017, 9(10), 483; doi:10.3390/polym9100483
Received: 28 August 2017 / Revised: 28 September 2017 / Accepted: 29 September 2017 / Published: 2 October 2017
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Abstract
Amphiphilic block-copolymers are known to self-assemble into micelles and vesicles. In this paper, we discuss the multiple options between and beyond these boundaries using amphiphilic AB diblock and ABC triblock copolymers. We adjust the final structure reached by the composition of the mixture,
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Amphiphilic block-copolymers are known to self-assemble into micelles and vesicles. In this paper, we discuss the multiple options between and beyond these boundaries using amphiphilic AB diblock and ABC triblock copolymers. We adjust the final structure reached by the composition of the mixture, by the preparation temperature, and by varying the time-scale of formation. This leads to the formation of vesicles and micelles, but also internal micelles in larger sheets, lamellar vesicles, and closed tubes, thus broadening the amount of self-assembly structures available and deepening our understanding of them. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Synthesis and Characterization of Organosoluble, Thermal Stable and Hydrophobic Polyimides Derived from 4-(4-(1-pyrrolidinyl)phenyl)-2,6-bis(4-(4-aminophenoxy)phenyl)pyridine
Polymers 2017, 9(10), 484; doi:10.3390/polym9100484
Received: 4 September 2017 / Revised: 29 September 2017 / Accepted: 30 September 2017 / Published: 3 October 2017
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Abstract
A novel aromatic diamine monomer, 4-(4-(1-pyrrolidinyl)phenyl)-2,6-bis(4-(4-aminophenoxy)phenyl)pyridine (PPAPP) containing pyridine rings, pyrrolidine groups, and ether linkages, was successfully synthesized using 4-hydroxyacetophenone and 1-chloro-4-nitrobenzene as starting materials by three-step reactions, and then used to synthesize a series of polyimides by polycondensation with various aromatic dianhydrides
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A novel aromatic diamine monomer, 4-(4-(1-pyrrolidinyl)phenyl)-2,6-bis(4-(4-aminophenoxy)phenyl)pyridine (PPAPP) containing pyridine rings, pyrrolidine groups, and ether linkages, was successfully synthesized using 4-hydroxyacetophenone and 1-chloro-4-nitrobenzene as starting materials by three-step reactions, and then used to synthesize a series of polyimides by polycondensation with various aromatic dianhydrides via a two-step method. The structure of PPAPP was characterized by NMR, FT-IR, and mass spectrometry analysis methods. These polymers showed good solubility in common organic solvents (e.g., NMP, DMF, DMSO, and DMAc) at room temperature or on heating. Moreover, they presented a high thermal stability with the glass transition temperature (Tgs) exceeding 316 °C, as well as the temperature of 10% weight loss ranged from 552–580 °C with more than 67% residue at 800 °C under nitrogen. Furthermore, they also exhibited excellent hydrophobicity with a contact angle in the range of 85.6°–97.7°, and the results of Wide-Angle X-ray Diffraction (WAXD) indicated that all of the polymers revealed an amorphous structure. Full article
(This article belongs to the Special Issue High Performance Polymers)
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Open AccessArticle Controlled Release of Lysozyme from Double-Walled Poly(Lactide-Co-Glycolide) (PLGA) Microspheres
Polymers 2017, 9(10), 485; doi:10.3390/polym9100485
Received: 19 September 2017 / Revised: 28 September 2017 / Accepted: 28 September 2017 / Published: 3 October 2017
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Abstract
Double-walled microspheres based on poly(lactide-co-glycolide) (PLGA) are potential delivery systems for reducing a very high initial burst release of encapsulated protein and peptide drugs. In this study, double-walled microspheres made of glucose core, hydroxyl-terminated poly(lactide-co-glycolide) (Glu-PLGA), and carboxyl-terminated PLGA
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Double-walled microspheres based on poly(lactide-co-glycolide) (PLGA) are potential delivery systems for reducing a very high initial burst release of encapsulated protein and peptide drugs. In this study, double-walled microspheres made of glucose core, hydroxyl-terminated poly(lactide-co-glycolide) (Glu-PLGA), and carboxyl-terminated PLGA were fabricated using a modified water-in-oil-in-oil-in-water (w1/o/o/w2) emulsion solvent evaporation technique for the controlled release of a model protein, lysozyme. Microspheres size, morphology, encapsulation efficiency, lysozyme in vitro release profiles, bioactivity, and structural integrity, were evaluated. Scanning electron microscopy (SEM) images revealed that double-walled microspheres comprising of Glu-PLGA and PLGA with a mass ratio of 1:1 have a spherical shape and smooth surfaces. A statistically significant increase in the encapsulation efficiency (82.52% ± 3.28%) was achieved when 1% (w/v) polyvinyl alcohol (PVA) and 2.5% (w/v) trehalose were incorporated in the internal and external aqueous phase, respectively, during emulsification. Double-walled microspheres prepared together with excipients (PVA and trehalose) showed a better control release of lysozyme. The released lysozyme was fully bioactive, and its structural integrity was slightly affected during microspheres fabrication and in vitro release studies. Therefore, double-walled microspheres made of Glu-PLGA and PLGA together with excipients (PVA and trehalose) provide a controlled and sustained release for lysozyme. Full article
(This article belongs to the Special Issue Emulsion Polymerization)
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Open AccessArticle Polymer Blending as a Novel Approach for Tuning the SPR Peaks of Silver Nanoparticles
Polymers 2017, 9(10), 486; doi:10.3390/polym9100486
Received: 9 September 2017 / Revised: 29 September 2017 / Accepted: 30 September 2017 / Published: 4 October 2017
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Abstract
In the present work, a novel method is exhibited for tuning the surface plasmon resonance (SPR) peaks of silver nanoparticles based on chitosan-Poly(vinyl alcohol) blend polymer nanocomposites. Silver nanoparticles were synthesized by in situ method through the chitosan host polymer. The absence of
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In the present work, a novel method is exhibited for tuning the surface plasmon resonance (SPR) peaks of silver nanoparticles based on chitosan-Poly(vinyl alcohol) blend polymer nanocomposites. Silver nanoparticles were synthesized by in situ method through the chitosan host polymer. The absence of crystalline peaks of PVA in the blend system indicated the occurrence of miscibility between CS and PVA polymers. The UV–vis spectra of CS:AgNt samples shows SPR bands with weak intensity. Obvious tuning in SPR peaks of silver nanoparticles occurred when different amounts of PVA polymer incorporated to the CS:AgNt system. The appearance of distinguishable crystalline peaks of Ag° nanoparticles at 2θ = 38.6° and 2θ = 44.2° in the blend system reveals the role of polymer blending in the enhancement of SPR peaks of silver nanoparticles. Silver nanoparticles synthesized in this work with enhanced SPR peaks are important in various applications and areas such as optoelectronic devices. The TEM images show dispersed silver nanoparticles. The dielectric constant of PVA is higher than that of chitosan. The result of dielectric constant study validates the Mie model which reveals the fact that the dielectric constant of the surrounding material has a great effect on the SPR peak intensity of nanoparticles. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle Incorporation of Calcium Containing Mesoporous (MCM-41-Type) Particles in Electrospun PCL Fibers by Using Benign Solvents
Polymers 2017, 9(10), 487; doi:10.3390/polym9100487
Received: 10 July 2017 / Revised: 19 September 2017 / Accepted: 26 September 2017 / Published: 4 October 2017
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Abstract
The electrospinning technique is a versatile method for the production of fibrous scaffolds able to resemble the morphology of the native extra cellular matrix. In the present paper, electrospinning is used to fabricate novel SiO2 particles (type MCM-41) containing poly(epsilon-caprolactone) (PCL) fibers. The
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The electrospinning technique is a versatile method for the production of fibrous scaffolds able to resemble the morphology of the native extra cellular matrix. In the present paper, electrospinning is used to fabricate novel SiO2 particles (type MCM-41) containing poly(epsilon-caprolactone) (PCL) fibers. The main aims of the present work are both the optimization of the particle synthesis and the fabrication of composite fibers, obtained using benign solvents, suitable as drug delivery systems and scaffolds for soft tissue engineering applications. The optimized synthesis and characterization of calcium-containing MCM-41 particles are reported. Homogeneous bead-free composite electrospun mats were obtained by using acetic acid and formic acid as solvents; neat PCL electrospun mats were used as control. Initially, an optimization of the electrospinning environmental parameters, like relative humidity, was performed. The obtained composite nanofibers were characterized from the morphological, chemical and mechanical points of view, the acellular bioactivity of the composite nanofibers was also investigated. Positive results were obtained in terms of mesoporous particle incorporation in the fibers and no significant differences in terms of average fiber diameter were detected between the neat and composite electrospun fibers. Even if the Ca-containing MCM-41 particles are bioactive, this property is not preserved in the composite fibers. In fact, during the bioactivity assessment, the particles were released confirming the potential application of the composite fibers as a drug delivery system. Preliminary in vitro tests with bone marrow stromal cells were performed to investigate cell adhesion on the fabricated composite mats, the positive obtained results confirmed the suitability of the composite fibers as scaffolds for soft tissue engineering. Full article
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Open AccessArticle Cluster Formation of Polyphilic Molecules Solvated in a DPPC Bilayer
Polymers 2017, 9(10), 488; doi:10.3390/polym9100488
Received: 15 September 2017 / Revised: 29 September 2017 / Accepted: 29 September 2017 / Published: 6 October 2017
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Abstract
We analyse the initial stages of cluster formation of polyphilic additive molecules which are solvated in a dipalmitoylphosphatidylcholine (DPPC) lipid bilayer. Our polyphilic molecules comprise an aromatic (trans-bilayer) core domain with (out-of-bilayer) glycerol terminations, complemented with a fluorophilic and an alkyl side chain,
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We analyse the initial stages of cluster formation of polyphilic additive molecules which are solvated in a dipalmitoylphosphatidylcholine (DPPC) lipid bilayer. Our polyphilic molecules comprise an aromatic (trans-bilayer) core domain with (out-of-bilayer) glycerol terminations, complemented with a fluorophilic and an alkyl side chain, both of which are confined within the aliphatic segment of the bilayer. Large-scale molecular dynamics simulations (1 μ s total duration) of a set of six of such polyphilic additives reveal the initial steps towards supramolecular aggregation induced by the specific philicity properties of the molecules. For our intermediate system size of six polyphiles, the transient but recurrent formation of a trimer is observed on a characteristic timescale of about 100 ns. The alkane/perfluoroalkane side chains show a very distinct conformational distribution inside the bilayer thanks to their different philicity, despite their identical anchoring in the trans-bilayer segment of the polyphile. The diffusive mobility of the polyphilic additives is about the same as that of the surrounding lipids, although it crosses both bilayer leaflets and tends to self-associate. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Micron-Sized Pored Membranes Based on Polyvinylidene Difluoride Hexafluoropropylene Prepared by Phase Inversion Techniques
Polymers 2017, 9(10), 489; doi:10.3390/polym9100489
Received: 21 August 2017 / Revised: 15 September 2017 / Accepted: 27 September 2017 / Published: 6 October 2017
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Abstract
In this study, micron-sized pored membranes, based on the co-polymer polyvinylidene difluoride hexafluoropropylene (PVdF-HFP) were prepared via phase inversion techniques. The aim of the approach was to find less harmful and less toxic solvents to fabricate such films. Therefore, the Hansen solubility approach
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In this study, micron-sized pored membranes, based on the co-polymer polyvinylidene difluoride hexafluoropropylene (PVdF-HFP) were prepared via phase inversion techniques. The aim of the approach was to find less harmful and less toxic solvents to fabricate such films. Therefore, the Hansen solubility approach was used to identify safer and less toxic organic solvents for the phase inversion process, relative to present solvent mixtures, based on acetone, dimethyl formamide, dimethyl acetamide or methanol. With this approach, it was possible to identify cyclopentanone, ethylene glycol and benzyl alcohol as suitable solvents for the membrane preparation process. Physicochemical and mechanical properties were analyzed and compared, which revealed a uniform membrane structure through the cross section. Differences were observed at the top surface, in dependence of both preparation approaches, which are described in detail. Full article
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Open AccessArticle Preparation of Isotactic Polypropylene/Exfoliated MoS2 Nanocomposites via In Situ Intercalative Polymerization
Polymers 2017, 9(10), 490; doi:10.3390/polym9100490
Received: 22 September 2017 / Revised: 30 September 2017 / Accepted: 30 September 2017 / Published: 7 October 2017
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Abstract
In this research, a Ziegler–Natta catalyst intercalated MoS2 was synthesized through the intercalation of a Grignard reagent into MoS2 galleries, followed by the anchoring of TiCl4. During propylene polymerization, the intercalated MoS2 exfoliated in situ to form PP/exfoliated MoS2
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In this research, a Ziegler–Natta catalyst intercalated MoS2 was synthesized through the intercalation of a Grignard reagent into MoS2 galleries, followed by the anchoring of TiCl4. During propylene polymerization, the intercalated MoS2 exfoliated in situ to form PP/exfoliated MoS2 (EMoS2) nanocomposites. The isotactic index values of the resultant PP/EMoS2 nanocomposites were as high as 99%, varying from 98.1% to 99.0%. It was found that the incorporation of the EMoS2 significantly improved the thermal stability and mechanical properties (tensile strength, modulus, and elongation at break) of PP. After introduction of EMoS2, the maximum increases in Td5% and Tdmax were 36.9 and 9.7 °C, respectively, relative to neat PP. After blending with commercial PP, the resultant nanocomposites increase in tensile strength and modulus up to 11.4% and 61.2% after 0.52 wt % EMoS2 loading. Thus, this work provides a new way to produce high-performance PP. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessArticle Ferrocene-Modified Block Copolymers for the Preparation of Smart Porous Membranes
Polymers 2017, 9(10), 491; doi:10.3390/polym9100491
Received: 24 September 2017 / Revised: 5 October 2017 / Accepted: 5 October 2017 / Published: 8 October 2017
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Abstract
The design of artificially generated channels featuring distinct remote-switchable functionalities is of critical importance for separation, transport control, and water filtration applications. Here, we focus on the preparation of block copolymers (BCPs) consisting of polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) having molar
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The design of artificially generated channels featuring distinct remote-switchable functionalities is of critical importance for separation, transport control, and water filtration applications. Here, we focus on the preparation of block copolymers (BCPs) consisting of polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) having molar masses in the range of 91 to 124 kg mol−1 with a PHEMA content of 13 to 21 mol %. The BCPs can be conveniently functionalized with redox-active ferrocene moieties by a postmodification protocol for the hydrophilic PHEMA segments. Up to 66 mol % of the hydroxyl functionalities can be efficiently modified with the reversibly redox-responsive units. For the first time, the ferrocene-containing BCPs are shown to form nanoporous integral asymmetric membranes by self-assembly and application of the non-solvent-induced phase separation (SNIPS) process. Open porous structures are evidenced by scanning electron microscopy (SEM) and water flux measurements, while efficient redox-switching capabilities are investigated after chemical oxidation of the ferrocene moieties. As a result, the porous membranes reveal a tremendously increased polarity after oxidation as reflected by contact angle measurements. Additionally, the initial water flux of the ferrocene-containing membranes decreased after oxidizing the ferrocene moieties because of oxidation-induced pore swelling of the membrane. Full article
(This article belongs to the Special Issue Polymers and Block Copolymers at Interfaces and Surfaces)
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Open AccessArticle Synthesis and Characterization of Multifunctional Two-Component Waterborne Polyurethane Coatings: Fluorescence, Thermostability and Flame Retardancy
Polymers 2017, 9(10), 492; doi:10.3390/polym9100492
Received: 27 August 2017 / Revised: 25 September 2017 / Accepted: 30 September 2017 / Published: 8 October 2017
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Abstract
Fluorescent and flame-retardant two-component waterborne polyurethane coatings were synthesized using 1,5-dihydroxy naphthalene, a halogen-free polyphosphate and a hydrophilic curing agent, and their properties were systematically characterized. The average particle sizes and zeta potential values were below 170 nm and −30 mV. Meanwhile, the
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Fluorescent and flame-retardant two-component waterborne polyurethane coatings were synthesized using 1,5-dihydroxy naphthalene, a halogen-free polyphosphate and a hydrophilic curing agent, and their properties were systematically characterized. The average particle sizes and zeta potential values were below 170 nm and −30 mV. Meanwhile, the multifunctional two-component waterborne polyurethane coatings had strong fluorescence intensities. When comparing with the coatings with 0.5 wt % 1,5-dihydroxy naphthalene, the coatings with 1.0 wt % 1,5-dihydroxy naphthalene had a stronger microphase separation. Interestingly, the thermostability of the multifunctional coatings was remarkably improved through 1.0 wt % 1,5-dihydroxy naphthalene, and besides it belonged to nonflammable materials. Additionally, all of the coating films passed the solvent resistance testing. These samples with different amounts of 1,5-dihydroxy naphthalene are environmental friendly, especially applications that require transparent and fluorescent coatings. Full article
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Open AccessArticle Surface Properties of a Novel Poly(vinyl alcohol) Film Prepared by Heterogeneous Saponification of Poly(vinyl acetate) Film
Polymers 2017, 9(10), 493; doi:10.3390/polym9100493
Received: 2 August 2017 / Revised: 28 September 2017 / Accepted: 6 October 2017 / Published: 9 October 2017
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Abstract
Almost general poly(vinyl alcohol) (PVA) films were prepared by the processing of a PVA solution. For the first time, a novel poly(vinyl alcohol) (PVA) film was prepared by the saponification of a poly(vinyl acetate) (PVAc) film in a heterogenous medium. Under the same
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Almost general poly(vinyl alcohol) (PVA) films were prepared by the processing of a PVA solution. For the first time, a novel poly(vinyl alcohol) (PVA) film was prepared by the saponification of a poly(vinyl acetate) (PVAc) film in a heterogenous medium. Under the same saponification conditions, the influence of saponification time on the degree of saponification (DS) was studied for the preparation of the saponified PVA film, and it was found that the DS varied with time. Optical microscopy was used to confirm the characteristics and surface morphology of the saponified PVA film, revealing unusual black globules in the film structure. The contact angle of the films was measured to study the surface properties, and the results showed that the saponified PVA film had a higher contact angle than the general PVA film. To confirm the transformation of the PVAc film to the PVA film, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction measurements, differential scanning calorimetry, and Fourier-transform infrared spectroscopy were employed. Full article
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Open AccessArticle Isolation and Characterization of Cellulose from Different Fruit and Vegetable Pomaces
Polymers 2017, 9(10), 495; doi:10.3390/polym9100495
Received: 18 September 2017 / Revised: 29 September 2017 / Accepted: 30 September 2017 / Published: 9 October 2017
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Abstract
A new fractionation process was developed to achieve valorization of fruit and vegetable pomaces. The importance of the residues from fruits and vegetables is still growing; therefore; the study presents the novel route of a fractioning process for the conversion of agro-industrial biomasses,
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A new fractionation process was developed to achieve valorization of fruit and vegetable pomaces. The importance of the residues from fruits and vegetables is still growing; therefore; the study presents the novel route of a fractioning process for the conversion of agro-industrial biomasses, such as pomaces, into useful feedstocks with potential application in the fields of fuels, chemicals, and polymers. Hence, the biorefinery process is expected to convert them into various by-products offering a great diversity of low-cost materials. The final product of the process is the cellulose of the biofuel importance. The study presents the novel route of the fractioning process for the conversion of agro-industrial biomasses, such as pomaces, into useful feedstocks with a potential application in the fields of fuels, chemicals, and polymers. Therefore the aim of this paper was to present the novel route of the pomaces fraction and the characterization of residuals. Pomaces from apple, cucumber, carrot, and tomato were treated sequentially with water, acidic solution, alkali solution, and oxidative reagent in order to obtain fractions reach in sugars, pectic polysaccharides, hemicellulose, cellulose, and lignin. Pomaces were characterized by dry matter content, neutral detergent solubles, hemicellulose, cellulose, and lignin. Obtained fractions were characterized by the content of pectins expressed as galacturonic acid equivalent and hemicelluloses expressed as a xyloglucan equivalent. The last fraction and residue was cellulose characterized by crystallinity degree by X-ray diffractometer (XRD), microfibril diameter by atomic force microscope (AFM), and overall morphology by scanning electron microscope (SEM). The hemicelluloses content was similar in all pomaces. Moreover, all the materials were characterized by the high pectins level in extracts evaluated as galacturonic acid content. The lignins content compared with other plant biomasses was on a very low level. The cellulose fraction was the highest in cucumber pomace. The cellulose fraction was characterized by crystallinity degree, microfibril diameter, and overall morphology. Isolated cellulose had a very fine structure with relatively high crystalline index but small crystallites. Full article
(This article belongs to the Special Issue Polysaccharides)
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Open AccessArticle Facile Synthesis of Electroactive and Electrochromic Triptycene Poly(ether-imide)s Containing Triarylamine Units via Oxidative Electro-Coupling
Polymers 2017, 9(10), 497; doi:10.3390/polym9100497
Received: 11 September 2017 / Revised: 8 October 2017 / Accepted: 8 October 2017 / Published: 10 October 2017
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Abstract
Two bisimide compounds, TPA–TPDI and NPC–TPDI, consisting of a triptycene core and two triphenylamine (TPA) or N-phenylcarbazole (NPC) end groups were successfully synthesized by the condensation reactions from 1,4-bis(3,4-dicarboxyphenoxy)triptycene dianhydride with 4-aminotriphenylamine and N-(4-aminophenyl)carbazole, respectively. These two monomers could polymerize electrochemically via the
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Two bisimide compounds, TPA–TPDI and NPC–TPDI, consisting of a triptycene core and two triphenylamine (TPA) or N-phenylcarbazole (NPC) end groups were successfully synthesized by the condensation reactions from 1,4-bis(3,4-dicarboxyphenoxy)triptycene dianhydride with 4-aminotriphenylamine and N-(4-aminophenyl)carbazole, respectively. These two monomers could polymerize electrochemically via the oxidative coupling reactions of triarylamine units. The electrochemical and spectroelectrochemical properties of the electro-generated triptycene poly(ether-imide)s (TPA–TPPI and NPC–TPPI) were studied. Both polymers have two colored oxidation states, and TPA–TPPI showed better electrochromic performance than NPC–TPPI. Full article
(This article belongs to the Special Issue High Performance Polymers)
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Open AccessArticle Microwave-Assisted Synthesis of Nanoporous Aluminum-Based Coordination Polymers as Catalysts for Selective Sulfoxidation Reaction
Polymers 2017, 9(10), 498; doi:10.3390/polym9100498
Received: 23 September 2017 / Revised: 1 October 2017 / Accepted: 3 October 2017 / Published: 11 October 2017
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Abstract
A series of aluminum-based coordination polymers or metal–organic frameworks (Al–MOFs), i.e., DUT-4, DUT-5, MIL-53, NH2-MIL-53, and MIL-100, have been facile prepared by microwave (MW)-assisted reactions and used as catalysts for selective sulfoxidation reactions. The MW-assisted synthesis drastically reduced the reaction time
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A series of aluminum-based coordination polymers or metal–organic frameworks (Al–MOFs), i.e., DUT-4, DUT-5, MIL-53, NH2-MIL-53, and MIL-100, have been facile prepared by microwave (MW)-assisted reactions and used as catalysts for selective sulfoxidation reactions. The MW-assisted synthesis drastically reduced the reaction time from few days to hours. The prepared MOFs have smaller and uniform particle sizes and better yield compared to conventional hydrothermal method. Furthermore, the Al–MOFs have been successfully demonstrated as catalysts in oxidation reaction of methyl phenyl sulfide with H2O2 as oxidant, even under mild conditions, with more than 95% conversion. Full article
(This article belongs to the Special Issue Coordination Polymer)
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Open AccessArticle Influence of Polymer Relaxation Time on the Electrospinning Process: Numerical Investigation
Polymers 2017, 9(10), 501; doi:10.3390/polym9100501
Received: 20 September 2017 / Revised: 30 September 2017 / Accepted: 8 October 2017 / Published: 12 October 2017
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Abstract
“Electrospinnability”, or the ease with which a solution can be used to obtain bead-free uniform fibers, depends on a large number of parameters, including solution properties, process parameters and ambient conditions. In this study, the effect of the polymer relaxation time on electrospinning
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“Electrospinnability”, or the ease with which a solution can be used to obtain bead-free uniform fibers, depends on a large number of parameters, including solution properties, process parameters and ambient conditions. In this study, the effect of the polymer relaxation time on electrospinning of dilute polymer solutions is investigated numerically. It is shown that elastic stresses (ES) increase exponentially with the Deborah number ( D e ). For each polymer concentration there exists a critical D e below which the ES are insufficient to overcome capillary stresses (CS) and lead to the formation of beaded fibers. However, above the critical D e , there is a higher probability of the ES overcoming the CS and leading to the formation of uniform fibers. This analysis suggests the possibility of improved electrospinnability even with dilute polymer solutions, provided the relaxation time is sufficiently large. It is also found that changes in the drag coefficient due to change in the polymer conformation and self-concentration of polymer molecules would become significant for the electrospinning of polymer solutions with a longer relaxation time and high conductivity. Full article
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Open AccessArticle Fabrication of Al2O3 Nano-Structure Functional Film on a Cellulose Insulation Polymer Surface and Its Space Charge Suppression Effect
Polymers 2017, 9(10), 502; doi:10.3390/polym9100502
Received: 20 September 2017 / Revised: 5 October 2017 / Accepted: 7 October 2017 / Published: 12 October 2017
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Abstract
Cellulose insulation polymer (paper/pressboard) has been widely used in high voltage direct current (HVDC) transformers. One of the most challenging issues in the insulation material used for HVDC equipment is the space charge accumulation. Effective ways to suppress the space charge injection/accumulation in
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Cellulose insulation polymer (paper/pressboard) has been widely used in high voltage direct current (HVDC) transformers. One of the most challenging issues in the insulation material used for HVDC equipment is the space charge accumulation. Effective ways to suppress the space charge injection/accumulation in insulation material is currently a popular research topic. In this study, an aluminium oxide functional film was deposited on a cellulose insulation pressboard surface using reactive radio frequency (RF) magnetron sputtering. The sputtered thin film was characterized by the scanning electron microscopy/energy dispersive spectrometer (SEM/EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The influence of the deposited functional film on the dielectric properties and the space charge injection/accumulation behaviour was investigated. A preliminary exploration of the space charge suppression effect is discussed. SEM/EDS, XPS, and XRD results show that the nano-structured Al2O3 film with amorphous phase was successfully fabricated onto the fibre surface. The cellulose insulation pressboard surface sputtered by Al2O3 film has lower permittivity, conductivity, and dissipation factor values in the lower frequency (<103 Hz) region. The oil-impregnated sputtered pressboard presents an apparent space-charge suppression effect. Compared with the pressboard sputtered with Al2O3 film for 90 min, the pressboard sputtered with Al2O3 film for 60 min had a better space charge suppression effect. Ultra-small Al2O3 particles (<10 nm) grew on the surface of the larger nanoparticles. The nano-structured Al2O3 film sputtered on the fibre surface could act as a functional barrier layer for suppression of the charge injection and accumulation. This study offers a new perspective in favour of the application of insulation pressboard with a nano-structured function surface against space charge injection/accumulation in HVDC equipment. Full article
(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)
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Open AccessArticle Supramolecular Interactions Induce Unexpectedly Strong Emissions from Triphenylamine-Functionalized Polytyrosine Blended with Poly(4-vinylpyridine)
Polymers 2017, 9(10), 503; doi:10.3390/polym9100503
Received: 12 September 2017 / Revised: 2 October 2017 / Accepted: 10 October 2017 / Published: 12 October 2017
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Abstract
In this study, we synthesized a triphenylamine-functionalized polytyrosine (PTyr-TPA) through living ring opening polymerization with 4,4′-diamino-4″-methoxytriphenylamine (TPA-NH2) as an initiator, and used Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy to confirm the chemical structure. Photoluminescence spectroscopy revealed the photophysical
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In this study, we synthesized a triphenylamine-functionalized polytyrosine (PTyr-TPA) through living ring opening polymerization with 4,4′-diamino-4″-methoxytriphenylamine (TPA-NH2) as an initiator, and used Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy to confirm the chemical structure. Photoluminescence spectroscopy revealed the photophysical properties of TPA-NH2 and PTyr-TPA and suggested that TPA-NH2 exhibited aggregation-caused quenching; in contrast, attaching the initiator to the rigid rod conformation of the PTyr segments caused PTyr-TPA to display aggregation-induced emission behavior. Differential scanning calorimetry revealed single glass transition temperatures for miscible PTyr-TPA/P4VP blends, the result of intermolecular hydrogen bonding between the pyridine units of P4VP and the phenolic OH units of PTyr-TPA, as confirmed through FTIR spectroscopic analyses. Furthermore, the chain behavior of PTyr-TPA transformed from a β-sheet conformation to random coils after blending with P4VP, as determined using wide-angle X-ray diffraction. These findings suggest that the decreased emission intensity of PTyr-TPA resulted from release of the restricted intramolecular rotation of the triphenylamine moiety in the polypeptide center. Full article
(This article belongs to the Special Issue Smart Polymers)
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Open AccessArticle Interfacial Hydrogen Bonds and Their Influence Mechanism on Increasing the Thermal Stability of Nano-SiO2-Modified Meta-Aramid Fibres
Polymers 2017, 9(10), 504; doi:10.3390/polym9100504
Received: 19 September 2017 / Revised: 9 October 2017 / Accepted: 9 October 2017 / Published: 12 October 2017
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Abstract
For further analysis of the effect of nano-doping on the properties of high polymers and research into the mechanism behind modified interfacial hydrogen bonds, a study on the formation probability of nano-SiO2/meta-aramid fibre interfacial hydrogen bonds and the strengthening mechanism behind
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For further analysis of the effect of nano-doping on the properties of high polymers and research into the mechanism behind modified interfacial hydrogen bonds, a study on the formation probability of nano-SiO2/meta-aramid fibre interfacial hydrogen bonds and the strengthening mechanism behind interfacial hydrogen bonds on the thermal stability of meta-aramid fibres using molecular dynamics is performed in this paper. First, the pure meta-aramid fibre and nano-SiO2/meta-aramid fibre mixed models with nanoparticle radiuses of 3, 5, 7 and 9 Å (1 Å = 10−1 nm) are built, and then the optimization process and dynamics simulation of the models are conducted. The dynamics simulation results indicate that the number of hydrogen bonds increase due to the doping by nano-SiO2 and that the number of interfacial hydrogen bonds increases with the nanoparticle radius. By analysing the hydrogen bond formation probability of all the atom pairs in the mixed model with pair correlation functions (PCFs), it can be observed that the hydrogen bond formation probability between the oxygen atom and hydrogen atom on the nanoparticle surface is the greatest. An effective way to increase the number of interfacial hydrogen bonds in nano-SiO2 and meta-aramid fibres is to increase the number of hydrogen atoms on the nano-silica surface and oxygen atoms in the meta-aramid fibre. By using the radial distribution function (RDF), the conclusion can be further drawn that the hydrogen bond formation probability is at a maximum when the atomic distance is 2.7–2.8 Å; therefore, increasing the number of atoms within this range can significantly increase the formation probability of hydrogen bonds. According to the results of chain movement, the existence of interfacial hydrogen bonds effectively limits the free movement of the molecular chains of meta-aramid fibres and enhances the thermal stability of meta-aramid fibres. The existence of interfacial hydrogen bonds is one of the important reasons for formation of the stable interface structure between nanoparticles and meta-aramid fibres. In addition, a nanoparticle with a small radius improves the interfacial hydrogen bond energy density and interfacial interaction energy density, enhancing the stability of the mixed model interface. Full article
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Open AccessFeature PaperArticle Correlating PSf Support Physicochemical Properties with the Formation of Piperazine-Based Polyamide and Evaluating the Resultant Nanofiltration Membrane Performance
Polymers 2017, 9(10), 505; doi:10.3390/polym9100505
Received: 25 August 2017 / Revised: 4 October 2017 / Accepted: 11 October 2017 / Published: 13 October 2017
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Abstract
Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200–35,000 g/mol). This alteration facilitated the formation of a thin
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Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200–35,000 g/mol). This alteration facilitated the formation of a thin polyamide layer on the PSf surface during the interfacial polymerization reaction involving an aqueous solution of piperazine containing 4-aminobenzoic acid and an organic solution of trimesoyl chloride. Attenuated total reflectance-Fourier transform infrared validated the presence of PEG in the membrane support. Scanning electron microscopy and atomic force microscopy illustrated that the thin-film polyamide layer morphology transformed from a rough to a smooth surface. A cross-flow filtration test indicated that a thin-film composite polyamide membrane comprising a PSf support (TFC-PEG20k) with a low surface porosity, small pore size, and suitable hydrophilicity delivered the highest water flux and separation efficiency (J = 81.1 ± 6.4 L·m−2·h−1, RNa2SO4 = 91.1% ± 1.8%, and RNaCl = 35.7% ± 3.1% at 0.60 MPa). This membrane had a molecular weight cutoff of 292 g/mol and also a high rejection for negatively charged dyes. Therefore, a PSf support exhibiting suitable physicochemical properties endowed a thin-film composite polyamide membrane with high performance. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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Open AccessArticle Spontaneous Formation of Fractal Aggregates of Au Nanoparticles in Epoxy-Siloxane Films and Their Application as Substrates for NIR Surface Enhanced Raman Spectroscopy
Polymers 2017, 9(10), 507; doi:10.3390/polym9100507
Received: 4 July 2017 / Revised: 18 September 2017 / Accepted: 20 September 2017 / Published: 13 October 2017
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Abstract
We present a facile, inexpensive route to free-standing, thermo-mechanically robust and flexible epoxy-siloxane substrates embedded with fractal aggregates of Au nanoparticles, and demonstrate their efficiency as substrates for surface enhanced Raman spectroscopy (SERS) at NIR wavelengths. The metallodielectric films are prepared by generating
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We present a facile, inexpensive route to free-standing, thermo-mechanically robust and flexible epoxy-siloxane substrates embedded with fractal aggregates of Au nanoparticles, and demonstrate their efficiency as substrates for surface enhanced Raman spectroscopy (SERS) at NIR wavelengths. The metallodielectric films are prepared by generating Au nanoparticles through the in-situ reduction of gold (III) chloride trihydrate in epoxypropoxypropyl terminated polydimethyl siloxane (EDMS). The metal nanoparticles spontaneously aggregate into fractal structures in the colloid, which could then be drop-cast onto a substrate. Subsequent UV-initiated cationic polymerization of epoxide moieties in EDMS transforms the fluid colloid into a thin, free-standing film, which contains a dense distribution of fractal aggregates of Au nanoparticles. We used electron and optical microscopy as well as UV–Vis–NIR spectrometry to monitor the evolution of nanoparticles and to optically and structurally characterize the resulting films. Raman spectroscopy of the chromophore Eosin Y adsorbed onto the metallodielectric films showed that they are excellent SERS substrates at NIR excitation with an enhancement factor of ~9.3 × 103. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle Evolution of Surface Nanopores in Pressurised Gyrospun Polymeric Microfibers
Polymers 2017, 9(10), 508; doi:10.3390/polym9100508
Received: 19 September 2017 / Revised: 2 October 2017 / Accepted: 6 October 2017 / Published: 13 October 2017
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Abstract
The selection of a solvent or solvent system and the ensuing polymer–solvent interactions are crucial factors affecting the preparation of fibers with multiple morphologies. A range of poly(methylmethacrylate) fibers were prepared by pressurised gyration using acetone, chloroform, N,N-dimethylformamide (DMF), ethyl acetate and
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The selection of a solvent or solvent system and the ensuing polymer–solvent interactions are crucial factors affecting the preparation of fibers with multiple morphologies. A range of poly(methylmethacrylate) fibers were prepared by pressurised gyration using acetone, chloroform, N,N-dimethylformamide (DMF), ethyl acetate and dichloromethane as solvents. It was found that microscale fibers with surface nanopores were formed when using chloroform, ethyl acetate and dichloromethane and poreless fibers were formed when using acetone and DMF as the solvent. These observations are explained on the basis of the physical properties of the solvents and mechanisms of pore formation. The formation of porous fibers is caused by many solvent properties such as volatility, solubility parameters, vapour pressure and surface tension. Cross-sectional images show that the nanopores are only on the surface of the fibers and they were not inter-connected. Further, the results show that fibers with desired nanopores (40–400 nm) can be prepared by carefully selecting the solvent and applied pressure in the gyration process. Full article
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Open AccessArticle The Effect of Heat Transfer and Polymer Concentration on Non-Newtonian Fluid from Pore-Scale Simulation of Rock X-ray Micro-CT
Polymers 2017, 9(10), 509; doi:10.3390/polym9100509
Received: 14 September 2017 / Revised: 9 October 2017 / Accepted: 11 October 2017 / Published: 13 October 2017
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Abstract
Most of the pore-scale imaging and simulations of non-Newtonian fluid are based on the simplifying geometry of network modeling and overlook the fluid rheology and heat transfer. In the present paper, we developed a non-isothermal and non-Newtonian numerical model of the flow properties
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Most of the pore-scale imaging and simulations of non-Newtonian fluid are based on the simplifying geometry of network modeling and overlook the fluid rheology and heat transfer. In the present paper, we developed a non-isothermal and non-Newtonian numerical model of the flow properties at pore-scale by simulation of the 3D micro-CT images using a Finite Volume Method (FVM). The numerical model is based on the resolution of the momentum and energy conservation equations. Owing to an adaptive mesh generation technique and appropriate boundary conditions, rock permeability and mobility are accurately computed. A temperature and concentration-dependent power-law viscosity model in line with the experimental measurement of the fluid rheology is adopted. The model is first applied at isothermal condition to 2 benchmark samples, namely Fontainebleau sandstone and Grosmont carbonate, and is found to be in good agreement with the Lattice Boltzmann method (LBM). Finally, at non-isothermal conditions, an effective mobility is introduced that enables to perform a numerical sensitivity study to fluid rheology, heat transfer, and operating conditions. While the mobility seems to evolve linearly with polymer concentration in agreement with a derived theoretical model, the effect of the temperature seems negligible by comparison. However, a sharp contrast is found between carbonate and sandstone under the effect of a constant temperature gradient. Besides concerning the flow index and consistency factor, a master curve is derived when normalizing the mobility for both the carbonate and the sandstone. Full article
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Open AccessArticle Facile Synthesis of Polyaniline Nanotubes with Square Capillary Using Urea as Template
Polymers 2017, 9(10), 510; doi:10.3390/polym9100510
Received: 27 September 2017 / Revised: 10 October 2017 / Accepted: 12 October 2017 / Published: 14 October 2017
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Abstract
Polyaniline nanotubes were successfully synthesized by a facile in situ chemical oxidative polymerization method using urea as soft template. When the urea/aniline molar ratio is 3:1, the as-prepared nanotubular polyaniline (PANI-3) shows regular and uniform square capillaries, which provides a high electrode/electrolyte contact,
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Polyaniline nanotubes were successfully synthesized by a facile in situ chemical oxidative polymerization method using urea as soft template. When the urea/aniline molar ratio is 3:1, the as-prepared nanotubular polyaniline (PANI-3) shows regular and uniform square capillaries, which provides a high electrode/electrolyte contact, easy ion diffusion and enhanced electroactive regions during the electrochemical process, leading to weak internal resistance and improved electrochemical performance. The PANI-3 sample exhibits a high specific capacitance of 405 F/g at current density of 0.2 A/g, and PANI only has a specific capacitance of 263 F/g. At current density of 1 A/g, the capacitance of PANI-3 is still 263 F/g (64.9% of the capacitance at 0.2 A/g). Such a PANI-3 nanotube, with regular and uniform capillary, is a promising electrode material for high-performance supercapacitors. Full article
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Open AccessArticle Synthesis and Electrochromism of Highly Organosoluble Polyamides and Polyimides with Bulky Trityl-Substituted Triphenylamine Units
Polymers 2017, 9(10), 511; doi:10.3390/polym9100511
Received: 5 September 2017 / Revised: 7 October 2017 / Accepted: 12 October 2017 / Published: 14 October 2017
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Abstract
Two series of polyamides and polyimides containing bulky trityl-substituted triphenylamine units were synthesized from condensation reactions of 4,4′-diamino-4′′-trityltriphenylamine with various dicarboxylic acids and tetracarboxylic dianhydrides, respectively. The polymers showed good solubility and film-forming ability. Flexible or robust films could be readily obtained via
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Two series of polyamides and polyimides containing bulky trityl-substituted triphenylamine units were synthesized from condensation reactions of 4,4′-diamino-4′′-trityltriphenylamine with various dicarboxylic acids and tetracarboxylic dianhydrides, respectively. The polymers showed good solubility and film-forming ability. Flexible or robust films could be readily obtained via solution-casting. The use of aliphatic diacid or dianhydride reduces interchain charge transfer complexing and leads to colorless polyamide and polyimide films. These polymers showed glass-transition temperatures in the range of 206–336 °C. Cyclic voltammograms of the polyamide and polyimide films displayed reversible electrochemical oxidation processes in the range of 0–1.0 or 0–1.3 V. Upon oxidation, the color of polymer films changes from colorless to blue-green or blue. As compared to the polyimide counterparts, the polyamides showed lower oxidation potentials and thus a higher electrochromic stability and coloration efficiency. Simple electrochromic devices were also fabricated as a preliminary investigation for electrochromic applications of the prepared polymers. Full article
(This article belongs to the Special Issue High Performance Polymers)
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Open AccessArticle Conjugated Polymers Containing BODIPY and Fluorene Units for Sensitive Detection of CN Ions: Site-Selective Synthesis, Photo-Physical and Electrochemical Properties
Polymers 2017, 9(10), 512; doi:10.3390/polym9100512
Received: 11 September 2017 / Revised: 9 October 2017 / Accepted: 10 October 2017 / Published: 14 October 2017
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Abstract
Conjugated polymers containing distinct molecular units are expected to be very interesting because of their unique properties endowed by these units and the formed conjugated polymers. Herein, four new conjugated copolymers based on fluorene and 4,4’-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) have been designed and
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Conjugated polymers containing distinct molecular units are expected to be very interesting because of their unique properties endowed by these units and the formed conjugated polymers. Herein, four new conjugated copolymers based on fluorene and 4,4’-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) have been designed and synthesized via Sonogashira polymerization. The fluorene unit was attached to the 3,5- or 2,6-positions of BODIPY by ethynylenes or p-diacetylenebenzene. The obtained polymers show good thermal stability and broad absorption in the wavelength range from 300 to 750 nm. The effects of site-selective copolymerization and conjugation length along the polymer backbone on the optoelectronic and electrochemical properties of these copolymers were systematically studied by UV-Vis spectroscopy, photoluminescence (PL) and cyclic voltammetry. Besides, it is found that the BODIPY-based copolymers exhibit selectively sensitive responses to cyanide anions, resulting in obvious change of UV-Vis absorption spectra and significant fluorescence quenching of the polymers among various common anions. Full article
(This article belongs to the Special Issue Conjugated Polymers 2016)
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Open AccessArticle A Low-Cost, Formaldehyde-Free and High Flame Retardancy Wood Adhesive from Inorganic Adhesives: Properties and Performance
Polymers 2017, 9(10), 513; doi:10.3390/polym9100513
Received: 13 September 2017 / Revised: 11 October 2017 / Accepted: 11 October 2017 / Published: 16 October 2017
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Abstract
Wood composites used in indoor living environments often pose formaldehyde emission and fire hazard problems. In this study, magnesium oxychloride cement-based (MOC) inorganic adhesives are presented as an effective and sustainable binder for plywood applications. The phase composition, microstructure, and thermal stability of
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Wood composites used in indoor living environments often pose formaldehyde emission and fire hazard problems. In this study, magnesium oxychloride cement-based (MOC) inorganic adhesives are presented as an effective and sustainable binder for plywood applications. The phase composition, microstructure, and thermal stability of the adhesives prepared with different ratios of MgO/MgCl2 were investigated. In addition, the dry and wet shear strength and the combustion behavior of the plywood were also examined. The results indicated that the limiting oxygen index (LOI) values of the plywood bonded by the MOC adhesives were higher than those of the plywood bonded by urea-formaldehyde resin. The active MgO/MgCl2 molar ratio of 7 was the optimal ratio for the dry and wet shear strength of the plywood with values of 1.02 and 0.88 MPa, respectively, which meet the interior use panel (Type II plywood) requirements. These improvements were ascribed to the increasing ratio of MgO/MgCl2 that facilitated the formation of an excellent microstructure. Meanwhile, the continuous hydration phase strengthened the interaction between the MOC adhesive and the wood. With these improved properties, MOC adhesive is expected to be widely used for industrial applications in plywood fabrication. Full article
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Open AccessArticle Characterization and Performance of Soy-Based Adhesives Cured with Epoxy Resin
Polymers 2017, 9(10), 514; doi:10.3390/polym9100514
Received: 27 August 2017 / Revised: 2 October 2017 / Accepted: 12 October 2017 / Published: 16 October 2017
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Abstract
Soy-based adhesives have attracted much attention recently because they are environmentally safe, low cost, and readily available. To improve the gluability and water resistance of soy-based adhesives, we prepared an enzyme-treated soy-based adhesive modified with an epoxy resin. We investigated the wet shear
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Soy-based adhesives have attracted much attention recently because they are environmentally safe, low cost, and readily available. To improve the gluability and water resistance of soy-based adhesives, we prepared an enzyme-treated soy-based adhesive modified with an epoxy resin. We investigated the wet shear strength of plywood bonded with the modified adhesive using the boiling-water test. Fourier transformed infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance analysis were used to characterize the reaction between epoxy groups and –NH2 groups in the modified soy-based adhesives. FTIR analysis confirmed the cross-linking structure in the cured adhesives. Viscosity and the solid content of soy-based adhesives gradually increased with the increasing amount of epoxy resin, but had little effect on its operability. Wet shear strength of plywood samples increased as the amount of epoxy resin was increased, whereas the inverse trend was observed regarding the water absorption of cured adhesives. Compared to an unmodified adhesive, the addition of 30% of epoxy resin increased the wet shear strength of plywood samples by 58.3% (0.95 MPa), meeting the requirement of the Chinese National Standard for exterior plywood. Differential scanning calorimetry and thermogravimetric analysis showed the improved thermostability of the cured adhesives after curing at 160 °C. These results suggest that epoxy resin could effectively improve the performance of enzyme-treated soy-based adhesives, which might provide a new option for the preparation of soy-based adhesives with high gluability and water resistance. Full article
(This article belongs to the collection Polymeric Adhesives)
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Open AccessArticle A Single-Site Iron(III)-Salan Catalyst for Converting COS to Sulfur-Containing Polymers
Polymers 2017, 9(10), 515; doi:10.3390/polym9100515 (registering DOI)
Received: 22 September 2017 / Revised: 9 October 2017 / Accepted: 11 October 2017 / Published: 17 October 2017
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Abstract
An iron(III) complex of tetradentate N,N′-disubstituted bis(aminophenoxide) (designated as salan, a saturated version of the corresponding salen ligand) with a sterically hindered organic base anchored on the ligand framework, can selectively mediate the conversion of carbonyl sulfide to sulfur-containing polymers
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An iron(III) complex of tetradentate N,N′-disubstituted bis(aminophenoxide) (designated as salan, a saturated version of the corresponding salen ligand) with a sterically hindered organic base anchored on the ligand framework, can selectively mediate the conversion of carbonyl sulfide to sulfur-containing polymers by the copolymerization with epoxides. This single-site catalyst exhibits broad substrate scope, and the resultant copolymers have completely alternating structures. In addition, this catalyst is efficient in producing diblock copolymers, suggesting a living polymerization nature. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessFeature PaperArticle Medium Bandgap D-A Type Photovoltaic Polymers Based on an Asymmetric Dithienopyran Donor and a Benzotriazole Acceptor
Polymers 2017, 9(10), 516; doi:10.3390/polym9100516 (registering DOI)
Received: 20 September 2017 / Revised: 11 October 2017 / Accepted: 12 October 2017 / Published: 17 October 2017
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Abstract
Conjugated polymers based on the donor of an asymmetric 5H-dithieno[3,2-b:2′,3′-d]pyran (DTPa) and the acceptors of benzo[d][1,2,3]triazole (BTA) or di-fluorinated benzo[d][1,2,3]triazole (ffBTA) with thiophene as π-bridge were designed and synthesized. Two asymmetric-building-block-containing polymers (ABC-polymers) possess a
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Conjugated polymers based on the donor of an asymmetric 5H-dithieno[3,2-b:2′,3′-d]pyran (DTPa) and the acceptors of benzo[d][1,2,3]triazole (BTA) or di-fluorinated benzo[d][1,2,3]triazole (ffBTA) with thiophene as π-bridge were designed and synthesized. Two asymmetric-building-block-containing polymers (ABC-polymers) possess a strong and broad absorption in the range of 300–750 nm and medium optical bandgap of 1.73 and 1.77 eV for PDTPa-TBTA and PDTPa-TffBTA, respectively. Polymer solar cells using PDTPa-TBTA as donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an acceptor exhibited power conversion efficiencies (PCE) of 2.22% with a Voc of 0.58 V, a Jsc of 6.04 mA/cm2, and an FF of 63.41%. The introduction of fluorine substituents on the BTA unit evidently influenced the optical and photovoltaic properties. Interestingly, although the HOMO energy level indeed decreased, PDTPa-TffBTA showed a decreased Voc of 0.52 V in solar cells. Combined with an obviously enhanced Jsc of 10.23 mA/cm2, and an outstanding FF of 0.64, the PCE of solar cells based on PDTPa-TffBTA was improved by nearly 55%, reached 3.43%. Our results indicate that the BTA unit can be used to construct ABC polymers with a medium bandgap, and the introduction of fluorine on the BTA unit is also effective in improving the photovoltaic performance. Full article
(This article belongs to the Special Issue Polymer Solar Cells)
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Open AccessArticle Interactions of Biocidal Polyhexamethylene Guanidine Hydrochloride and Its Analogs with POPC Model Membranes
Polymers 2017, 9(10), 517; doi:10.3390/polym9100517 (registering DOI)
Received: 14 September 2017 / Revised: 5 October 2017 / Accepted: 11 October 2017 / Published: 17 October 2017
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Abstract
The bacterial membrane-targeted polyhexamethylene guanidine hydrochloride (PHGH) and its novel analog polyoctamethylene guanidine hydrochloride (POGH) had excellent antimicrobial activities against antibiotics-resistant bacteria. However, the biocompatibility aspects of PHGH and POGH on the phospholipid membrane of the eukaryotic cell have not yet been considered.
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The bacterial membrane-targeted polyhexamethylene guanidine hydrochloride (PHGH) and its novel analog polyoctamethylene guanidine hydrochloride (POGH) had excellent antimicrobial activities against antibiotics-resistant bacteria. However, the biocompatibility aspects of PHGH and POGH on the phospholipid membrane of the eukaryotic cell have not yet been considered. Four chemically synthesized cationic oligoguanidine polymers containing alkyl group with different carbon chain lengths, including PHGH, POGH, and their two analogs, were used to determine their interactions with zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipids vesicles mimicking the eukaryotic cell membrane. Characterization was conducted by using bactericidal dynamics, hemolysis testing, calcein dye leakage, and isothermal titration calorimetry. Results showed that the gradually lengthened alkyl carbon chain of four oligoguanidine polymers increased the biocidal activity of the polymer, accompanied with the increased hemolytic activity, calcein dye leakage rate and the increased absolute value of the exothermic effect of polymer-POPC membrane interaction. The thermodynamic curve of the polymer-POPC membrane interaction exhibited a very weak exothermic effect and a poorly unsaturated titration curve, which indicated that four guanidine polymers had weak affinity for zwitterionic POPC vesicles. Generally, PHGH of four guanidine polymers had high biocidal activity and relatively high biocompatibility. This study emphasized that appropriate amphiphilicity balanced by the alkyl chain length, and the positive charge is important factor for the biocompatibility of cationic antimicrobial guanidine polymer. Both PHGH and POGH exhibited destructive power to phospholipid membrane of eukaryotic cell, which should be considered in their industry applications. Full article
(This article belongs to the Special Issue Antimicrobial Polymers)
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Open AccessArticle Electrosynthesis of Copolymers Based on 1,3,5-Tris(N-Carbazolyl)Benzene and 2,2′-Bithiophene and Their Applications in Electrochromic Devices
Polymers 2017, 9(10), 518; doi:10.3390/polym9100518 (registering DOI)
Received: 12 September 2017 / Revised: 13 October 2017 / Accepted: 13 October 2017 / Published: 17 October 2017
PDF Full-text (943 KB)
Abstract
Poly(1,3,5-tris(N-carbazolyl)benzene) (PtnCz) and three copolymers based on 1,3,5-tris(N-carbazolyl)benzene (tnCz) and 2,2′-bithiophene (bTp) were electrochemically synthesized. The anodic P(tnCz1-bTp2) film with a tnCz/bTp feed molar ratio of 1/2 showed four colors (light orange at 0.0 V, yellowish-orange at 0.7 V,
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Poly(1,3,5-tris(N-carbazolyl)benzene) (PtnCz) and three copolymers based on 1,3,5-tris(N-carbazolyl)benzene (tnCz) and 2,2′-bithiophene (bTp) were electrochemically synthesized. The anodic P(tnCz1-bTp2) film with a tnCz/bTp feed molar ratio of 1/2 showed four colors (light orange at 0.0 V, yellowish-orange at 0.7 V, yellowish-green at 0.8 V, and blue at 1.1 V) from the neutral state to oxidized states. The optical contrast (∆T%) and coloration efficiency (η) of the P(tnCz1-bTp2) film were measured as 48% and 112 cm2∙C1, respectively, at 696 nm. Electrochromic devices (ECDs) based on PtnCz, P(tnCz1-bTp1), P(tnCz1-bTp2), P(tnCz1-bTp4), and PbTp films as anodic polymer layers and poly(3,4-dihydro-3,3-dimethyl-2H-thieno[3,4-b-1,4]dioxepin) (PProDOT-Me2) as cathodic polymer layers were assembled. P(tnCz1-bTp2)/PProDOT-Me2 ECD showed three various colors (saffron yellow, yellowish-blue, and dark blue) at potentials ranging from −0.3 to 1.5 V. In addition, P(tnCz1-bTp2)/PProDOT-Me2 ECD showed a high ∆T% value (40% at 630 nm) and a high coloration efficiency (519 cm2∙C1 at 630 nm). Full article
(This article belongs to the Special Issue Smart Polymers)
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Open AccessArticle Modeling the Temperature Dependence of Dynamic Mechanical Properties and Visco-Elastic Behavior of Thermoplastic Polyurethane Using Artificial Neural Network
Polymers 2017, 9(10), 519; doi:10.3390/polym9100519 (registering DOI)
Received: 11 September 2017 / Revised: 12 October 2017 / Accepted: 15 October 2017 / Published: 18 October 2017
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Abstract
This paper presents one of the soft computing methods, specifically the artificial neural network technique, that has been used to model the temperature dependence of dynamic mechanical properties and visco-elastic behavior of widely exploited thermoplastic polyurethane over the wide range of temperatures. It
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This paper presents one of the soft computing methods, specifically the artificial neural network technique, that has been used to model the temperature dependence of dynamic mechanical properties and visco-elastic behavior of widely exploited thermoplastic polyurethane over the wide range of temperatures. It is very complex and commonly a highly non-linear problem with no easy analytical methods to predict them directly and accurately in practice. Variations of the storage modulus, loss modulus, and the damping factor with temperature were obtained from the dynamic mechanical analysis tests across transition temperatures at constant single frequency of dynamic mechanical loading. Based on dynamic mechanical analysis experiments, temperature dependent values of both dynamic moduli and damping factor were calculated by three models of well-trained multi-layer feed-forward back-propagation artificial neural network. The excellent agreement between the modeled and experimental data has been found over the entire investigated temperature interval, including all of the observed relaxation transitions. The multi-layer feed-forward back-propagation artificial neural network has been confirmed to be a very effective artificial intelligence tool for the modeling of dynamic mechanical properties and for the prediction of visco-elastic behavior of tested thermoplastic polyurethane in the whole temperature range of its service life. Full article
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Open AccessArticle Evaluation of Thermal and Thermomechanical Behaviour of Bio-Based Polyamide 11 Based Composites Reinforced with Lignocellulosic Fibres
Polymers 2017, 9(10), 522; doi:10.3390/polym9100522 (registering DOI)
Received: 14 September 2017 / Revised: 13 October 2017 / Accepted: 16 October 2017 / Published: 18 October 2017
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Abstract
In this work, polyamide 11 (PA11) and stone ground wood fibres (SGW) were used, as an alternative to non-bio-based polymer matrices and reinforcements, to obtain short fibre reinforced composites. The impact of the reinforcement on the thermal degradation, thermal transitions and microstructure of
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In this work, polyamide 11 (PA11) and stone ground wood fibres (SGW) were used, as an alternative to non-bio-based polymer matrices and reinforcements, to obtain short fibre reinforced composites. The impact of the reinforcement on the thermal degradation, thermal transitions and microstructure of PA11-based composites were studied. Natural fibres have lower degradation temperatures than PA11, thus, composites showed lower onset degradation temperatures than PA11, as well. The thermal transition and the semi-crystalline structure of the composites were similar to PA11. On the other hand, when SGW was submitted to an annealing treatment, the composites prepared with these fibres increased its crystallinity, with increasing fibre contents, compared to PA11. The differences between the glass transition temperatures of annealed and untreated composites decreased with the fibre contents. Thus, the fibres had a higher impact in the composites mechanical behaviour than on the mobility of the amorphous phase. The crystalline structure of PA11 and PA11-SGW composites, after annealing, was transformed to α’ more stable phase, without any negative impact on the properties of the fibres. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
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Open AccessArticle Microstructure and Performance of a Porous Polymer Membrane with a Copper Nano-Layer Using Vapor-Induced Phase Separation Combined with Magnetron Sputtering
Polymers 2017, 9(10), 524; doi:10.3390/polym9100524 (registering DOI)
Received: 14 September 2017 / Revised: 9 October 2017 / Accepted: 13 October 2017 / Published: 18 October 2017
PDF Full-text (8002 KB)
Abstract
Antibacterial metalized poly(vinylidene fluoride) (PVDF) porous membranes with a nano-layer were obtained via the method of vapor-induced phase separation combined with magnetron sputtering of copper. Magnetron sputtering has such advantages as high deposition rates, low substrate temperatures, and good adhesion of films on
[...] Read more.
Antibacterial metalized poly(vinylidene fluoride) (PVDF) porous membranes with a nano-layer were obtained via the method of vapor-induced phase separation combined with magnetron sputtering of copper. Magnetron sputtering has such advantages as high deposition rates, low substrate temperatures, and good adhesion of films on substrates. The influence brought by deposition time on the microstructure, hydrophobic property, copper distribution state, anti-biofouling, and permeation separation performance was investigated via atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) spectrometry, contact angle measurements, and capillary flow porometry, along with the porosity, water flux, protein solution flux, rejection rate, water flux recovery rate, and antibacterial property. The results showed that copper particles formed island-type deposits on the membrane surface and were embedded into cross-section pores near the surface owning to the interconnection of pores. Subsequently, the water flux and protein solution flux declined, but the rejection rate and water flux recovery rate increased. Meanwhile, Cu-coated PVDF membranes exhibited an excellent antibacterial ability. Full article
(This article belongs to the Special Issue Polymerizations from Surfaces)
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Open AccessArticle Perpendicular Structure Formation of Block Copolymer Thin Films during Thermal Solvent Vapor Annealing: Solvent and Thickness Effects
Polymers 2017, 9(10), 525; doi:10.3390/polym9100525 (registering DOI)
Received: 25 September 2017 / Revised: 13 October 2017 / Accepted: 13 October 2017 / Published: 18 October 2017
PDF Full-text (6152 KB)
Abstract
Solvent vapor annealing of block copolymer (BCP) thin films can produce a range of interesting morphologies, especially when the perpendicular orientation of micro-domains with respect to the substrate plays a role. This, for instance, allows BCP thin films to serve as useful templates
[...] Read more.
Solvent vapor annealing of block copolymer (BCP) thin films can produce a range of interesting morphologies, especially when the perpendicular orientation of micro-domains with respect to the substrate plays a role. This, for instance, allows BCP thin films to serve as useful templates for nanolithography and hybrid materials preparation. However, precise control of the arising morphologies is essential, but in most cases difficult to achieve. In this work, we investigated the solvent and thickness effects on the morphology of poly(styrene-b-2 vinyl pyridine) (PS-b-P2VP) thin films with a film thickness range from 0.4 L0 up to 0.8 L0. Ordered perpendicular structures were achieved. One of the main merits of our work is that the phase behavior of the ultra-high molecular weight BCP thin films, which hold a 100-nm sized domain distance, can be easily monitored via current available techniques, such as scanning electron microscope (SEM), atomic force microscope (AFM), and transmission electron microscope (TEM). Systematic monitoring of the self-assembly behavior during solvent vapor annealing can thus provide an experimental guideline for the optimization of processing conditions of related BCP films systems. Full article
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Open AccessArticle Facile Cellulose Dissolution and Characterization in the Newly Synthesized 1,3-Diallyl-2-ethylimidazolium Acetate Ionic Liquid
Polymers 2017, 9(10), 526; doi:10.3390/polym9100526 (registering DOI)
Received: 20 September 2017 / Revised: 9 October 2017 / Accepted: 13 October 2017 / Published: 18 October 2017
PDF Full-text (1203 KB) | Supplementary Files
Abstract
A facile cellulose solvent 1,3-diallyl-2-ethylimidazolium acetate ([AAeim][OAc]) with high electrical conductivity has been designed and synthesized for the first time, via a quaternization reaction and ion exchange method. The dissolution characteristics of cellulose in this solvent were studied in detail. Meanwhile, the co-solvent
[...] Read more.
A facile cellulose solvent 1,3-diallyl-2-ethylimidazolium acetate ([AAeim][OAc]) with high electrical conductivity has been designed and synthesized for the first time, via a quaternization reaction and ion exchange method. The dissolution characteristics of cellulose in this solvent were studied in detail. Meanwhile, the co-solvent system was designed by adding an aprotic polar solvent dimethyl sulfoxide (DMSO) in [AAeim][OAc]. The effects of temperature and the mass ratio of DMSO to [AAeim][OAc] on the solubility of cellulose were studied. Furthermore, the effects of regeneration on the molecular structure and thermal stability of cellulose were determined by Fourier transform infrared spectroscopy (FT-IR), thermal gravity analysis (TGA) and X-ray diffraction (XRD). The findings revealed that the synthesized ionic liquid (IL) has a relatively low viscosity, high conductivity and a good dissolving capacity for bamboo dissolving pulp cellulose (Degree of Polymerization: DP = 650). The macromolecular chain of the cellulose is less damaged during the dissolution and regeneration process. Due to the increased number of “free” anions [OAc]and cations [AAeim]+, the addition of DMSO can significantly increase the solubility of the cellulose up to 12 wt % at the mass ratio of 3:1, indicating that the synthesized IL has a potential application in the electrospinning field. Full article
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Review

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Open AccessReview Precise Synthesis of Macromolecular Architectures by Novel Iterative Methodology Combining Living Anionic Polymerization with Specially Designed Linking Chemistry
Polymers 2017, 9(10), 470; doi:10.3390/polym9100470
Received: 26 August 2017 / Revised: 16 September 2017 / Accepted: 17 September 2017 / Published: 25 September 2017
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Abstract
This article reviews the development of a novel all-around iterative methodology combining living anionic polymerization with specially designed linking chemistry for macromolecular architecture syntheses. The methodology is designed in such a way that the same reaction site is always regenerated after the polymer
[...] Read more.
This article reviews the development of a novel all-around iterative methodology combining living anionic polymerization with specially designed linking chemistry for macromolecular architecture syntheses. The methodology is designed in such a way that the same reaction site is always regenerated after the polymer chain is introduced in each reaction sequence, and this “polymer chain introduction and regeneration of the same reaction site” sequence is repeatable. Accordingly, the polymer chain can be successively and, in principle, limitlessly introduced to construct macromolecular architectures. With this iterative methodology, a variety of synthetically difficult macromolecular architectures, i.e., multicomponent μ-star polymers, high generation dendrimer-like hyperbranched polymers, exactly defined graft polymers, and multiblock polymers having more than three blocks, were successfully synthesized. Full article
(This article belongs to the Special Issue Living Polymerization)
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Open AccessReview The Chemistry and Physics of Bayfol® HX Film Holographic Photopolymer
Polymers 2017, 9(10), 472; doi:10.3390/polym9100472
Received: 7 August 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 26 September 2017
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Abstract
Holographic photopolymers are a new technology to create passive diffractive optical elements by a pure laser interference recording. In this review, we explain the chemistry concepts of light harvesting in an interference pattern and the subsequent grating formation as chemical response. Using the
[...] Read more.
Holographic photopolymers are a new technology to create passive diffractive optical elements by a pure laser interference recording. In this review, we explain the chemistry concepts of light harvesting in an interference pattern and the subsequent grating formation as chemical response. Using the example of the newly developed Bayfol® HX film we discuss the reaction-diffusion driven photo-polymerization process for an index modulation formation to create volume phase gratings. Further we elucidate the selection of monomer chemistry and discuss details of the recording conditions based on the concept of exposure dosage and exposure time. Influences ranging from high dosage recording to low power recording are explained and how to affect the desired diffraction efficiency. Finally, we outline and demonstrate the process to mass manufacturing of volume phase gratings. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessReview Block Copolymers: Synthesis, Self-Assembly, and Applications
Polymers 2017, 9(10), 494; doi:10.3390/polym9100494
Received: 19 September 2017 / Revised: 2 October 2017 / Accepted: 3 October 2017 / Published: 9 October 2017
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Abstract
Research on block copolymers (BCPs) has played a critical role in the development of polymer chemistry, with numerous pivotal contributions that have advanced our ability to prepare, characterize, theoretically model, and technologically exploit this class of materials in a myriad of ways in
[...] Read more.
Research on block copolymers (BCPs) has played a critical role in the development of polymer chemistry, with numerous pivotal contributions that have advanced our ability to prepare, characterize, theoretically model, and technologically exploit this class of materials in a myriad of ways in the fields of chemistry, physics, material sciences, and biological and medical sciences. The breathtaking progress has been driven by the advancement in experimental techniques enabling the synthesis and characterization of a wide range of block copolymers with tailored composition, architectures, and properties. In this review, we briefly discussed the recent progress in BCP synthesis, followed by a discussion of the fundamentals of self-assembly of BCPs along with their applications. Full article
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Open AccessReview Systematic Development Strategy for Smart Devices Based on Shape-Memory Polymers
Polymers 2017, 9(10), 496; doi:10.3390/polym9100496
Received: 24 September 2017 / Revised: 29 September 2017 / Accepted: 29 September 2017 / Published: 10 October 2017
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Abstract
Shape-memory polymers are outstanding “smart” materials, which can perform important geometrical changes, when activated by several types of external stimuli, and which can be applied to several emerging engineering fields, from aerospace applications, to the development of biomedical devices. The fact that several
[...] Read more.
Shape-memory polymers are outstanding “smart” materials, which can perform important geometrical changes, when activated by several types of external stimuli, and which can be applied to several emerging engineering fields, from aerospace applications, to the development of biomedical devices. The fact that several shape-memory polymers can be structured in an additive way is an especially noteworthy advantage, as the development of advanced actuators with complex geometries for improved performance can be achieved, if adequate design and manufacturing considerations are taken into consideration. Present study presents a review of challenges and good practices, leading to a straightforward methodology (or integration of strategies), for the development of “smart” actuators based on shape-memory polymers. The combination of computer-aided design, computer-aided engineering and additive manufacturing technologies is analyzed and applied to the complete development of interesting shape-memory polymer-based actuators. Aspects such as geometrical design and optimization, development of the activation system, selection of the adequate materials and related manufacturing technologies, training of the shape-memory effect, final integration and testing are considered, as key processes of the methodology. Current trends, including the use of low-cost 3D and 4D printing, and main challenges, including process eco-efficiency and biocompatibility, are also discussed and their impact on the proposed methodology is considered. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessFeature PaperReview Polymer Nanocomposites via Click Chemistry Reactions
Polymers 2017, 9(10), 499; doi:10.3390/polym9100499
Received: 29 September 2017 / Revised: 6 October 2017 / Accepted: 9 October 2017 / Published: 11 October 2017
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Abstract
The emerging areas of polymer nanocomposites, as some are already in use in industrial applications and daily commodities, have the potential of offering new technologies with all manner of prominent capabilities. The incorporation of nanomaterials into polymeric matrix provides significant improvements, such as
[...] Read more.
The emerging areas of polymer nanocomposites, as some are already in use in industrial applications and daily commodities, have the potential of offering new technologies with all manner of prominent capabilities. The incorporation of nanomaterials into polymeric matrix provides significant improvements, such as higher mechanical, thermal or electrical properties. In these materials, interface/interphase of components play a crucial role bringing additional features on the resulting nanocomposites. Among the various preparation strategies of such materials, an appealing strategy relies on the use of click chemistry concept as a multi-purpose toolbox for both fabrication and modulation of the material characteristics. This review aims to deliver new insights to the researchers of the field by noticing effective click chemistry-based methodologies on the preparation of polymer nanocomposites and their key applications such as optic, biomedical, coatings and sensor. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessFeature PaperReview Synthesis and Application of Aurophilic Poly(Cysteine) and Poly(Cysteine)-Containing Copolymers
Polymers 2017, 9(10), 500; doi:10.3390/polym9100500
Received: 7 September 2017 / Revised: 5 October 2017 / Accepted: 7 October 2017 / Published: 11 October 2017
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Abstract
The redox capacity, as well as the aurophilicity of the terminal thiol side groups, in poly(Cysteine) lend a unique characteristic to this poly(amino acid) or polypeptide. There are two major application fields for this polymer: (i) biomedical applications in drug delivery and surface
[...] Read more.
The redox capacity, as well as the aurophilicity of the terminal thiol side groups, in poly(Cysteine) lend a unique characteristic to this poly(amino acid) or polypeptide. There are two major application fields for this polymer: (i) biomedical applications in drug delivery and surface modification of biomedical devices and (ii) as coating for electrodes to enhance their electrochemical sensitivity. The intended application determines the synthetic route for p(Cysteine). Polymers to be used in biomedical applications are typically polymerized from the cysteine N-carboxyanhydride by a ring-opening polymerization, where the thiol group needs to be protected during the polymerization. Advances in this methodology have led to conditions under which the polymerization progresses as living polymerization, which allows for a strict control of the molecular architecture, molecular weight and polydispersity and the formation of block copolymers, which eventually could display polyphilic properties. Poly(Cysteine) used as electrode coating is typically polymerized onto the electrode by cyclic voltammetry, which actually produces a continuous, pinhole-free film on the electrode via the formation of covalent bonds between the amino group of Cysteine and the carbon of the electrode. This resulting coating is chemically very different from the well-defined poly(Cysteine) obtained by ring-opening polymerizations. Based on the structure of cysteine a significant degree of cross-linking within the coating deposited by cyclic voltammetry can be assumed. This manuscript provides a detailed discussion of the ring-opening polymerization of cysteine, a brief consideration of the role of glutathione, a key cysteine-containing tripeptide, and examples for the utilization of poly(Cysteine) and poly(Cysteine)-containing copolymers, in both, the biomedical as well as electrochemical realm. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessReview Synthesis, Morphologies and Building Applications of Nanostructured Polymers
Polymers 2017, 9(10), 506; doi:10.3390/polym9100506
Received: 8 September 2017 / Revised: 3 October 2017 / Accepted: 10 October 2017 / Published: 13 October 2017
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Abstract
Nanostructured polymers (NSPs) are polymeric materials in the size of nanoscale, normally consisting of nanoparticles, nanofibers, nanowires, nanospheres and other morphologies. Polymer nanoparticles (PNPs) can be fabricated either by physical methods (i.e., solvent evaporation, nanoprecipitation, salting out) or by direct nanosynthesis, using micro-
[...] Read more.
Nanostructured polymers (NSPs) are polymeric materials in the size of nanoscale, normally consisting of nanoparticles, nanofibers, nanowires, nanospheres and other morphologies. Polymer nanoparticles (PNPs) can be fabricated either by physical methods (i.e., solvent evaporation, nanoprecipitation, salting out) or by direct nanosynthesis, using micro- or nanoemulsions with nanoreactor compartments to perform polymerization. Polymer nanofibers (PNFs) can be produced via various techniques and the most commonly used approach is electrospinning, whereby a charged solution of a polymer when exposed to an opposite high electric field is pulled into long thin nanofibers. NSPs in general exhibit enhanced properties such as excellent structural and mechanical properties, making them promising candidates for some particular building applications. A variety of PNFs have been developed and used for noise and air pollution filtration. Moreover, PNFs can also be fabricated with phase change materials which are usually employed for thermal energy storage in construction industry. In this review, we will summarize the morphologies and nanosynthesis methods of NSPs, in particular, PNPs and PNFs. In addition, representative NSPs mainly used in construction are introduced for building applications. Full article
(This article belongs to the Special Issue High Performance Polymers)
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Open AccessReview Development of Solution-Processable, Optically Transparent Polyimides with Ultra-Low Linear Coefficients of Thermal Expansion
Polymers 2017, 9(10), 520; doi:10.3390/polym9100520 (registering DOI)
Received: 11 September 2017 / Revised: 3 October 2017 / Accepted: 3 October 2017 / Published: 18 October 2017
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Abstract
This paper reviews the development of new high-temperature polymeric materials applicable to plastic substrates in image display devices with a focus on our previous results. Novel solution-processable colorless polyimides (PIs) with ultra-low linear coefficients of thermal expansion (CTE) are proposed in this paper.
[...] Read more.
This paper reviews the development of new high-temperature polymeric materials applicable to plastic substrates in image display devices with a focus on our previous results. Novel solution-processable colorless polyimides (PIs) with ultra-low linear coefficients of thermal expansion (CTE) are proposed in this paper. First, the principles of the coloration of PI films are briefly discussed, including the influence of the processing conditions on the film coloration, as well as the chemical and physical factors dominating the low CTE characteristics of the resultant PI films to clarify the challenges in simultaneously achieving excellent optical transparency, a very high Tg, a very low CTE, and excellent film toughness. A possible approach of achieving these target properties is to use semi-cycloaliphatic PI systems consisting of linear chain structures. However, semi-cycloaliphatic PIs obtained using cycloaliphatic diamines suffer various problems during precursor polymerization, cyclodehydration (imidization), and film preparation. In particular, when using trans-1,4-cyclohexanediamine (t-CHDA) as the cycloaliphatic diamine, a serious problem emerges: salt formation in the initial stages of the precursor polymerization, which terminates the polymerization in some cases or significantly extends the reaction period. The system derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) and t-CHDA can be polymerized by a controlled heating method and leads to a PI film with relatively good properties, i.e., excellent light transmittance at 400 nm (T400 = ~80%), a high Tg (>300 °C), and a very low CTE (10 ppm·K−1). However, this PI film is somewhat brittle (the maximum elongation at break, εb max is about 10%). On the other hand, the combination of cycloaliphatic tetracarboxylic dianhydrides and aromatic diamines does not result in salt formation. The steric structures of cycloaliphatic tetracarboxylic dianhydrides significantly influence the polymerizability with aromatic diamines and the CTE values of the resultant PI films. For three isomers of hydrogenated pyromellitic dianhydride, the steric structure effect on the polymerizability and the properties of the PI films is discussed. 1,2,3,4-Cyclobutanetetracarboxylic dianhydride (CBDA) is a very unusual cycloaliphatic tetracarboxylic dianhydride that is suitable for reducing the CTE. For example, the PI system derived from CBDA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) yields a colorless PI film with a relatively low CTE (21 ppm·K−1). However, this PI is insoluble in common organic solvents, which means that it is neither solution-processable nor compatible with the chemical imidization process; furthermore, the film is somewhat brittle (εb < 10%). In addition, the effect of the film preparation route on the film properties is shown to be significant. Films prepared via chemical imidization always have higher optical transparency and lower CTE values than those prepared via the conventional two-step process (i.e., precursor casting and successive thermal imidization). These results suggest that compatibility with the chemical imidization process is the key for achieving our goal. To dramatically improve the solubility in the CBDA-based PI systems, a novel amide-containing aromatic diamine (AB-TFMB), which possesses the structural features of TFMB and 4,4′-diaminobenzanilide (DABA), is proposed. The CBDA(70);6FDA(30)/AB-TFMB copolymer has an ultra-low CTE (7.3 ppm·K−1), excellent optical transparency (T400 = 80.6%, yellowness index (YI) = 2.5, and haze = 1.5%), a very high Tg (329 °C), sufficient ductility (εb max > 30%), and good solution-processability. Therefore, this copolymer is a promising candidate for use as a novel coating-type plastic substrate material. This paper also discusses how the target properties can be achieved without the help of cycloaliphatic monomers. Thus, elaborate molecular design allows the preparation of highly transparent and low-CTE aromatic poly(amide imide) and poly(ester imide) systems. Full article
(This article belongs to the Special Issue High Performance Polymers)
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Open AccessReview The Recent Developments in Biobased Polymers toward General and Engineering Applications: Polymers that are Upgraded from Biodegradable Polymers, Analogous to Petroleum-Derived Polymers, and Newly Developed
Polymers 2017, 9(10), 523; doi:10.3390/polym9100523 (registering DOI)
Received: 31 August 2017 / Revised: 17 September 2017 / Accepted: 18 September 2017 / Published: 18 October 2017
PDF Full-text (1084 KB)
Abstract
The main motivation for development of biobased polymers was their biodegradability, which is becoming important due to strong public concern about waste. Reflecting recent changes in the polymer industry, the sustainability of biobased polymers allows them to be used for general and engineering
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The main motivation for development of biobased polymers was their biodegradability, which is becoming important due to strong public concern about waste. Reflecting recent changes in the polymer industry, the sustainability of biobased polymers allows them to be used for general and engineering applications. This expansion is driven by the remarkable progress in the processes for refining biomass feedstocks to produce biobased building blocks that allow biobased polymers to have more versatile and adaptable polymer chemical structures and to achieve target properties and functionalities. In this review, biobased polymers are categorized as those that are: (1) upgrades from biodegradable polylactides (PLA), polyhydroxyalkanoates (PHAs), and others; (2) analogous to petroleum-derived polymers such as bio-poly(ethylene terephthalate) (bio-PET); and (3) new biobased polymers such as poly(ethylene 2,5-furandicarboxylate) (PEF). The recent developments and progresses concerning biobased polymers are described, and important technical aspects of those polymers are introduced. Additionally, the recent scientific achievements regarding high-spec engineering-grade biobased polymers are presented. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)

Other

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Open AccessErratum Erratum: Correlation-Based Multiplexing of Complex Amplitude Data Pages in a Holographic Storage System Using Digital Holographic Techniques. Polymers, 2017, 9, 375
Polymers 2017, 9(10), 477; doi:10.3390/polym9100477
Received: 28 September 2017 / Revised: 29 September 2017 / Accepted: 29 September 2017 / Published: 29 September 2017
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Abstract
The authors wish to make a change to the published paper [1].[...] Full article

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