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Polymers, Volume 9, Issue 11 (November 2017)

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Cover Story A new copolymer with a temperature-responsive block and a cationic block was prepared by reversible [...] Read more.
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Open AccessArticle Formose Reaction Controlled by a Copolymer of N,N-Dimethylacrylamide and 4-Vinylphenylboronic Acid
Polymers 2017, 9(11), 549; doi:10.3390/polym9110549
Received: 8 October 2017 / Revised: 21 October 2017 / Accepted: 24 October 2017 / Published: 25 October 2017
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Abstract
The formose reaction is an oligomerization of formaldehyde under basic conditions, which produces a complicated mixture of monosaccharides and sugar alcohols. Selective formation of useful monosaccharides by the formose reaction has been an important challenge. In this study, we have investigated the formose
[...] Read more.
The formose reaction is an oligomerization of formaldehyde under basic conditions, which produces a complicated mixture of monosaccharides and sugar alcohols. Selective formation of useful monosaccharides by the formose reaction has been an important challenge. In this study, we have investigated the formose reaction controlled by N,N-dimethylacrylamide/4-vinylphenylboronic acid copolymer (pDMA/VBA) and phenylboronic acid (PBA) because boronic acid compounds form esters with polyols, e.g., monosaccharides and sugar alcohols. We obtained time–conversion data in the presence of these boronic acid compounds, and characterized the products by liquid chromatography-mass spectroscopy and NMR measurements. pDMA/VBA and PBA decelerated the formose reaction because of the formation of boronic acid esters with products. It is noteworthy that the formose reaction in the presence of pDMA/VBA and PBA formed favorably six- and seven-carbon branched monosaccharides and sugar alcohols. Full article
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Open AccessArticle Ion Conduction and Its Activation in Hydrated Solid Polyelectrolyte Complexes
Polymers 2017, 9(11), 550; doi:10.3390/polym9110550
Received: 28 August 2017 / Revised: 20 October 2017 / Accepted: 20 October 2017 / Published: 25 October 2017
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Abstract
For the first time, temperature-dependent conductivities at constant water content for a series of solid polyelectrolyte complexes with varying mixing ratios of anionic poly(sodium 4-styrene sulfonate) and poly(diallyldimethylammonium chloride) are presented. For water absorption, the samples are first equilibrated at an ambient temperature
[...] Read more.
For the first time, temperature-dependent conductivities at constant water content for a series of solid polyelectrolyte complexes with varying mixing ratios of anionic poly(sodium 4-styrene sulfonate) and poly(diallyldimethylammonium chloride) are presented. For water absorption, the samples are first equilibrated at an ambient temperature and at fixed relative humidity (RH). During the conductivity measurements, the so achieved water content of the samples is kept constant. At all of the hydration levels, the dc conductivities of the hydrated polyelectrolyte complexes (PEC) display Arrhenius behavior with activation enthalpies that are significantly lower than those of dry complexes. The activation enthalpy decreases linearly with water content. The lower activation enthalpies in case of hydrated as compared to dried complexes are attributed to a lowering of the energy barriers for ion motion. Finally, it is shown that the temperature-dependent conductivity spectra at constant water content obey the time-temperature superposition principle. Additionally, temperature-dependent conductivities at constant water content are compared to data sets determined in a separate study with constant RH at all of the temperatures. For the latter case, the influence of the type of alkali ion is also considered. Using the broad variety of data sets, the influences of water content and temperature on the conductivity mechanism can be separated from each other. Full article
(This article belongs to the Special Issue Ionic Polymers)
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Open AccessArticle Preparation, Characterization and Application of UV-Curable Flexible Hyperbranched Polyurethane Acrylate
Polymers 2017, 9(11), 552; doi:10.3390/polym9110552
Received: 28 September 2017 / Revised: 20 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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Abstract
A novel UV-curable hyperbranched polyurethane acrylate (FHBPUA) with excellent flexibility is successfully synthesized based on a reaction of hydroxyl terminated hyperbranched polyurethane (regarded as core) with flexible semiadduct urethane monoacrylate (regarded as arms). The structure and property of FHBPUA is firstly analyzed and
[...] Read more.
A novel UV-curable hyperbranched polyurethane acrylate (FHBPUA) with excellent flexibility is successfully synthesized based on a reaction of hydroxyl terminated hyperbranched polyurethane (regarded as core) with flexible semiadduct urethane monoacrylate (regarded as arms). The structure and property of FHBPUA is firstly analyzed and then utilized as functional additives to ameliorate the UV-curing and mechanical properties of epoxy acrylate resin. The degree of branching of FHBPUA turns out to be 0.82. Its thermal decomposition process consists of three different stages, and the glass transition temperature is around 65 °C. The freestanding FHBPUA film (~30 μm thickness) can be UV-cured within 3 s, and its flexibility is up to 1 mm. With the increase of FHBPUA content to 10 wt %, the UV-curing time of UV1000 film decreases from 6 to 3 s, flexibility strikingly increases from 10 to 1 mm, and adhesive force also improves from 5 to 3 grades, meanwhile its glossiness is not influenced by FHBPUA. In addition, a certain amount of FHBPUA can improve the tensile strength and elongation at break of UV1000 film. This novel FHBPUA can be used not only to develop flexible UV-curable freestanding films but also as functional additives to perfect other UV-curable compositions like coatings, inks and 3D printed parts. Full article
(This article belongs to the Special Issue Thermosets)
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Open AccessArticle Experimental Evidence of Large Amplitude pH Mediated Autonomous Chemomechanical Oscillation
Polymers 2017, 9(11), 554; doi:10.3390/polym9110554
Received: 29 September 2017 / Revised: 23 October 2017 / Accepted: 25 October 2017 / Published: 25 October 2017
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Abstract
Large amplitude autonomous chemomechanical oscillations were observed in a coupled system consisting of a porous pH-responsive hydrogel and a bromate-sulfite-manganese (II) pH oscillatory reaction. The porous structure effectively improves the chemomechanical response speed, and the negative feedback species of the bulk oscillation Mn
[...] Read more.
Large amplitude autonomous chemomechanical oscillations were observed in a coupled system consisting of a porous pH-responsive hydrogel and a bromate-sulfite-manganese (II) pH oscillatory reaction. The porous structure effectively improves the chemomechanical response speed, and the negative feedback species of the bulk oscillation Mn2+ takes part in the coupling by forming complex and physical crosslinks with the responsive group in the gel. It strengthens the porous gel by forming additional networks, which may contribute to sustaining the long-lasting chemomechanical oscillation. Additionally, the interaction between Mn2+ and the hydrogel alters the period of the oscillatory reaction due to its binding competition with H+, the positive feedback species. Full article
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Open AccessArticle Effect of Perfluoroalkyl Endgroups on the Interactions of Tri-Block Copolymers with Monofluorinated F-DPPC Monolayers
Polymers 2017, 9(11), 555; doi:10.3390/polym9110555
Received: 28 September 2017 / Revised: 20 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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Abstract
We studied the interaction of amphiphilic and triphilic polymers with monolayers prepared from F-DPPC (1-palmitoyl-2-(16-fluoropalmitoyl)-sn-glycero-3-phosphocholine), a phospholipid with a single fluorine atom at the terminus of the sn-2 chain, an analogue of dipalmitoyl-phosphatidylcholine (DPPC). The amphiphilic block copolymers contained a
[...] Read more.
We studied the interaction of amphiphilic and triphilic polymers with monolayers prepared from F-DPPC (1-palmitoyl-2-(16-fluoropalmitoyl)-sn-glycero-3-phosphocholine), a phospholipid with a single fluorine atom at the terminus of the sn-2 chain, an analogue of dipalmitoyl-phosphatidylcholine (DPPC). The amphiphilic block copolymers contained a hydrophobic poly(propylene oxide) block flanked by hydrophilic poly(glycerol monomethacrylate) blocks (GP). F-GP was derived from GP by capping both termini with perfluoro-n-nonyl segments. We first studied the adsorption of GP and F-GP to lipid monolayers of F-DPPC. F-GP was inserted into the monolayer up to a surface pressure Π of 42.4 mN m−1, much higher than GP (32.5 mN m−1). We then studied isotherms of lipid-polymer mixtures co-spread at the air-water interface. With increasing polymer content in the mixture a continuous shift of the onset of the liquid-expanded (LE) to liquid-condensed (LC) transition towards higher molecular and higher area per lipid molecule was observed. F-GP had a larger effect than GP indicating that it needed more space. At a Π-value of 32 mN m−1, GP was excluded from the mixed monolayer, whereas F-GP stayed in F-DPPC monolayers up to 42 mN m−1. F-GP is thus more stably anchored in the monolayer up to higher surface pressures. Images of mixed monolayers were acquired using different fluorescent probes and showed the presence of perfluorinated segments of F-GP at LE-LC domain boundaries. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Microstructural Origins of Nonlinear Response in Associating Polymers under Oscillatory Shear
Polymers 2017, 9(11), 556; doi:10.3390/polym9110556
Received: 29 June 2017 / Revised: 22 October 2017 / Accepted: 24 October 2017 / Published: 26 October 2017
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Abstract
The response of associating polymers with oscillatory shear is studied through large-scale simulations. A hybrid molecular dynamics (MD), Monte Carlo (MC) algorithm is employed. Polymer chains are modeled as a coarse-grained bead-spring system. Functionalized end groups, at both ends of the polymer chains,
[...] Read more.
The response of associating polymers with oscillatory shear is studied through large-scale simulations. A hybrid molecular dynamics (MD), Monte Carlo (MC) algorithm is employed. Polymer chains are modeled as a coarse-grained bead-spring system. Functionalized end groups, at both ends of the polymer chains, can form reversible bonds according to MC rules. Stress-strain curves show nonlinearities indicated by a non-ellipsoidal shape. We consider two types of nonlinearities. Type I occurs at a strain amplitude much larger than one, type II at a frequency at which the elastic storage modulus dominates the viscous loss modulus. In this last case, the network topology resembles that of the system at rest. The reversible bonds are broken and chains stretch when the system moves away from the zero-strain position. For type I, the chains relax and the number of reversible bonds peaks when the system is near an extreme of the motion. During the movement to the other extreme of the cycle, first a stress overshoot occurs, then a yield accompanied by shear-banding. Finally, the network restructures. Interestingly, the system periodically restores bonds between the same associating groups. Even though major restructuring occurs, the system remembers previous network topologies. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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Open AccessArticle Reducing the Amount of Catalyst in TEMPO-Oxidized Cellulose Nanofibers: Effect on Properties and Cost
Polymers 2017, 9(11), 557; doi:10.3390/polym9110557
Received: 22 September 2017 / Revised: 13 October 2017 / Accepted: 24 October 2017 / Published: 26 October 2017
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Abstract
Cellulose nanofibers (CNF) are interesting biopolymers that find numerous applications in different scientific and technological fields. However, manufacturing costs are still one of the main drawbacks for the industrial production of highly fibrillated, transparent CNF suspensions. In the present study, cellulose nanofibers were
[...] Read more.
Cellulose nanofibers (CNF) are interesting biopolymers that find numerous applications in different scientific and technological fields. However, manufacturing costs are still one of the main drawbacks for the industrial production of highly fibrillated, transparent CNF suspensions. In the present study, cellulose nanofibers were produced from bleached eucalyptus pulp via TEMPO-mediated oxidation with varying amounts of NaClO and passed through a high-pressure homogenizer. The CNFs were chemically and physically characterized; cellulose nanopapers were also produced to study tensile properties. Production costs were also calculated. Results indicated that CNF properties are strongly dependent on the carboxyl content. Manufacturing costs showed that chemicals, in particular TEMPO catalyst, represent a large part of the final cost of CNFs. In order to solve this problem, a set of samples were prepared where the amount of TEMPO was gradually reduced. Characterization of samples prepared in this way showed that not only were the costs reduced, but also that the final properties of the CNFs were not significantly affected when the amount of TEMPO was reduced to half. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Open AccessArticle A pH-Indicating Colorimetric Tough Hydrogel Patch towards Applications in a Substrate for Smart Wound Dressings
Polymers 2017, 9(11), 558; doi:10.3390/polym9110558
Received: 10 October 2017 / Revised: 22 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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Abstract
The physiological milieu of healthy skin is slightly acidic, with a pH value between 4 and 6, whereas for skin with chronic or infected wounds, the pH value is above 7.3. As testing pH value is an effective way to monitor the status
[...] Read more.
The physiological milieu of healthy skin is slightly acidic, with a pH value between 4 and 6, whereas for skin with chronic or infected wounds, the pH value is above 7.3. As testing pH value is an effective way to monitor the status of wounds, a novel smart hydrogel wound patch incorporating modified pH indicator dyes was developed in this study. Phenol red (PR), the dye molecule, was successfully modified with methacrylate (MA) to allow a copolymerization with the alginate/polyacrylamide (PAAm) hydrogel matrix. This covalent attachment prevented the dye from leaching out of the matrix. The prepared pH-responsive hydrogel patch exhibited a porous internal structure, excellent mechanical property, and high swelling ratio, as well as an appropriate water vapour transmission rate. Mechanical responses of alginate/P(AAm-MAPR) hydrogel patches under different calcium and water contents were also investigated to consider the case of exudate accumulation into hydrogels. Results showed that increased calcium amount and reduced water content significantly improved the Young’s modulus and elongation at break of the hydrogels. These characteristics indicated the suitability of hydrogels as wound dressing materials. When pH increased, the color of the hydrogel patches underwent a transition from yellow (pH 5, 6 and 7) to orange (7.4 and 8), and finally to red (pH 9). This range of color change matches the clinically-meaningful pH range of chronic or infected wounds. Therefore, our developed hydrogels could be applied as promising wound dressing materials to monitor the wound healing process by a simple colorimetric display, thus providing a desirable substrate for printed electronics for smart wound dressing. Full article
(This article belongs to the Special Issue Polymer-Based Flexible Printed Electronics and Sensors)
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Open AccessArticle Properties of Electrospun Nanofibers of Multi-Block Copolymers of [Poly-ε-caprolactone-b-poly(tetrahydrofuran-co-ε-caprolactone)]m Synthesized by Janus Polymerization
Polymers 2017, 9(11), 559; doi:10.3390/polym9110559
Received: 3 September 2017 / Revised: 15 October 2017 / Accepted: 21 October 2017 / Published: 27 October 2017
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Abstract
Novel biodegradable multiblock copolymers of [PCL-b-P(THF-co-CL)]m with PCL fractions of 53.3 and 88.4 wt % were prepared by Janus polymerization of ε-caprolactone (CL) and tetrahydrofuran (THF). Their electrospun mats were obtained with optimized parameters containing bead-free nanofibers whose
[...] Read more.
Novel biodegradable multiblock copolymers of [PCL-b-P(THF-co-CL)]m with PCL fractions of 53.3 and 88.4 wt % were prepared by Janus polymerization of ε-caprolactone (CL) and tetrahydrofuran (THF). Their electrospun mats were obtained with optimized parameters containing bead-free nanofibers whose diameters were between 290 and 520 nm. The mechanical properties of the nanofiber scaffolds were measured showing the tensile strength and strain at break of 8–10 MPa and 123–161%, respectively. Annealing improved their mechanical properties and their tensile strength and strain at break of the samples increased to 10–13 MPa and 267–338%, respectively. Due to the porous structure and crystallization in nanoscale confinement, the mechanical properties of the nanofiber scaffolds appeared as plastics, rather than as the elastomers observed in bulk thermal-molded film. Full article
(This article belongs to the Special Issue Polymers and Block Copolymers at Interfaces and Surfaces)
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Open AccessArticle Studying the Drug Delivery Kinetics of a Nanoporous Matrix Using a MIP-Based Thermal Sensing Platform
Polymers 2017, 9(11), 560; doi:10.3390/polym9110560
Received: 11 October 2017 / Revised: 24 October 2017 / Accepted: 26 October 2017 / Published: 28 October 2017
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Abstract
The implementation of Molecularly Imprinted Polymers (MIPs) into sensing systems has been demonstrated abundantly over the past few decades. In this article, a novel application for an MIP-based thermal sensing platform is introduced by using the sensor to characterize the drug release kinetics
[...] Read more.
The implementation of Molecularly Imprinted Polymers (MIPs) into sensing systems has been demonstrated abundantly over the past few decades. In this article, a novel application for an MIP-based thermal sensing platform is introduced by using the sensor to characterize the drug release kinetics of a nanoporous silver-organic framework. This Ag nanoporous matrix was loaded with acetylsalicylic acid (aspirin) which was used as a model drug compound in this study. The drug elution properties were studied by placing the nanoporous matrix in phosphate buffered saline solution for two days and measuring the drug concentration at regular time intervals. To this extent, an acrylamide-based MIP was synthesized that was able to detect aspirin in a specific and selective manner. Rebinding of the template to the MIP was analyzed using a thermal sensor platform. The results illustrate that the addition of aspirin into the sensing chamber leads to a concentration-dependent increase in the phase shift of a thermal wave that propagates through the MIP-coated sensor chip. After constructing a dose-response curve, this system was used to study the drug release kinetics of the nanoporous matrix, clearly demonstrating that the metalorganic framework releases the drug steadily over the course of the first hour, after which the concentration reaches a plateau. These findings were further confirmed by UV–Visible spectroscopy, illustrating a similar time-dependent release in the same concentration range, which demonstrates that the MIP-based platform can indeed be used as a low-cost straightforward tool to assess the efficacy of drug delivery systems in a lab environment. Full article
(This article belongs to the Special Issue Molecularly Imprinted Polymers)
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Open AccessArticle Effect of Cellulose Nanocrystals and Bacterial Cellulose on Disintegrability in Composting Conditions of Plasticized PHB Nanocomposites
Polymers 2017, 9(11), 561; doi:10.3390/polym9110561
Received: 27 September 2017 / Revised: 23 October 2017 / Accepted: 26 October 2017 / Published: 28 October 2017
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Abstract
Poly(hydroxybutyrate) (PHB)-based films, reinforced with bacterial cellulose (BC) or cellulose nanocrystals (CNC) and plasticized using a molecular (tributyrin) or a polymeric plasticizer (poly(adipate diethylene)), were produced by solvent casting. Their morphological, thermal, wettability, and chemical properties were investigated. Furthermore, the effect of adding
[...] Read more.
Poly(hydroxybutyrate) (PHB)-based films, reinforced with bacterial cellulose (BC) or cellulose nanocrystals (CNC) and plasticized using a molecular (tributyrin) or a polymeric plasticizer (poly(adipate diethylene)), were produced by solvent casting. Their morphological, thermal, wettability, and chemical properties were investigated. Furthermore, the effect of adding both plasticizers (20 wt % respect to the PHB content) and biobased selected nanofillers added at different contents (2 and 4 wt %) on disintegrability in composting conditions was studied. Results of contact angle measurements and calorimetric analysis validated the observed behavior during composting experiments, indicating how CNC aggregation, due to the hydrophilic nature of the filler, slows down the degradation rate but accelerates it in case of increasing content. In contrast, nanocomposites with BC presented an evolution in composting similar to neat PHB, possibly due to the lower hydrophilic character of this material. The addition of the two plasticizers contributed to a better dispersion of the nanoparticles by increasing the interaction between the cellulosic reinforcements and the matrix, whereas the increased crystallinity of the incubated samples in a second stage in composting provoked a reduction in the disintegration rate. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle Towards Flexible Dielectric Materials with High Dielectric Constant and Low Loss: PVDF Nanocomposites with both Homogenously Dispersed CNTs and Ionic Liquids Nanodomains
Polymers 2017, 9(11), 562; doi:10.3390/polym9110562
Received: 1 September 2017 / Revised: 16 October 2017 / Accepted: 26 October 2017 / Published: 28 October 2017
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Abstract
Flexible dielectric materials with high dielectric constant and low loss have attracted significant attention. In this work, we fabricated novel polymer-based nanocomposites with both homogeneously dispersed conductive nanofillers and ion-conductive nanodomains within a polymer matrix. An unsaturated ionic liquid (IL), 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM][BF
[...] Read more.
Flexible dielectric materials with high dielectric constant and low loss have attracted significant attention. In this work, we fabricated novel polymer-based nanocomposites with both homogeneously dispersed conductive nanofillers and ion-conductive nanodomains within a polymer matrix. An unsaturated ionic liquid (IL), 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM][BF4]), was first coated on the surface of multi-walled carbon nanotubes (CNTs) by the mechanical grinding. The ILs coated CNTs were then well dispersed in poly(vinylidene fluoride) (PVDF) matrix by melt-blending. The ILs on the surface of CNTs were subsequently grafted onto the PVDF chains by electron beam irradiation (EBI). The formed ILs grafted PVDF (PVDF-g-IL) finally aggregated into ionic nanodomains with the size of 20–30 nm in the melt state. Therefore, novel PVDF nanocomposites with both homogenously dispersed CNTs and ionic nanodomains were achieved. Both carbon nanotubes and ionic nanodomains contributed to the enhancement of the dielectric constant of PVDF significantly. At the same time, such homogeneously dispersed CNTs along with the confined ions in the nandomains decreased current leakage effectively and thus led to the low dielectric loss. The final PVDF nanocomposites exhibited high dielectric constant, low dielectric loss and good flexibility, which may be promising for applications in soft/flexible devices. Full article
(This article belongs to the Special Issue Fluorinated Polymers)
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Open AccessArticle A Facile and Effective Method to Fabricate Superhydrophobic/Superoeophilic Surface for the Separation of Both Water/Oil Mixtures and Water-in-Oil Emulsions
Polymers 2017, 9(11), 563; doi:10.3390/polym9110563
Received: 30 September 2017 / Revised: 23 October 2017 / Accepted: 27 October 2017 / Published: 30 October 2017
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Abstract
Superhydrophobic/superoleophilic surfaces (water contact angle greater than 150° with low hysteresis, with an oil contact angle smaller than 5°) have a wide-range of applications in oil/water separation. However, most of the essential methods to fabricate this kind of surface are complex, inflexible, and
[...] Read more.
Superhydrophobic/superoleophilic surfaces (water contact angle greater than 150° with low hysteresis, with an oil contact angle smaller than 5°) have a wide-range of applications in oil/water separation. However, most of the essential methods to fabricate this kind of surface are complex, inflexible, and costly. Moreover, most methods focus on separating immiscible oil and water mixtures but lack the ability to demulsify surfactant-stabilized emulsions, which is widely present in industry and daily life. In this study, a facile and effective method was developed to fabricate superhydrophobic/superoleophilic surfaces that can be easily applied on almost all kinds of solid substrates. The treated porous substrates (e.g., steel mesh; cotton) can separate oil/water mixtures or absorb oil from a mixture. Furthermore, the compressed treated cotton is capable of demulsifying stabilized water-in-oil emulsions with high efficiency. The simple, low-cost, and material-unrestricted method provides an efficient way to separate oil/water mixtures of various kinds and has great potential in energy conservation and environmental protection. Full article
(This article belongs to the Special Issue Polymers and Block Copolymers at Interfaces and Surfaces)
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Open AccessArticle Synthesis of Hybrid-Polypeptides m-PEO-b-poly(His-co-Gly) and m-PEO-b-poly(His-co-Ala) and Study of Their Structure and Aggregation. Influence of Hydrophobic Copolypeptides on the Properties of Poly(L-histidine)
Polymers 2017, 9(11), 564; doi:10.3390/polym9110564
Received: 27 September 2017 / Revised: 23 October 2017 / Accepted: 23 October 2017 / Published: 30 October 2017
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Abstract
The highly diverse and sophisticated action of proteins results from their equally diverse primary structure, which along with the nature of interactions between the amino acids, defines the higher self-assembly of proteins. The interactions between amino acids can be very complicated, and their
[...] Read more.
The highly diverse and sophisticated action of proteins results from their equally diverse primary structure, which along with the nature of interactions between the amino acids, defines the higher self-assembly of proteins. The interactions between amino acids can be very complicated, and their understanding is necessary in order to elucidate the protein structure-properties relationship. A series of well-defined hybrid-polypeptidic diblock copolymers of the type m-PEO-b-poly(His-co-Gly) and m-PEO-b-poly(His-co-Ala) was synthesized through the ring opening polymerization of the N-carboxyanhydrides of the corresponding amino acids, with a molar ratio of the hydrophobic peptide to histidine at 10%, 20% and 40%. The excellent purity of the monomers combined with the high vacuum techniques resulted in controlled polymerization with high molecular and compositional homogeneity. FT-IR, as well as circular dichroism, were employed to investigate the secondary structure of the polymers, while DLS, SLS and ζ-potential were utilized to study the aggregates formed in aqueous solutions, as well as their pH responsiveness. The results revealed that the randomly distributed monomeric units of glycine or alanine significantly influence L-histidine’s structure. Depending on the pH, aggregates with a different structure, different molecular characteristics and a different surface charge are formed, potentially leading to very interesting bioapplications. Full article
(This article belongs to the Special Issue Polypeptide Containing Polymers)
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Open AccessArticle Direct Formation of Sub-Micron and Nanoparticles of a Bioinspired Coordination Polymer Based on Copper with Adenine
Polymers 2017, 9(11), 565; doi:10.3390/polym9110565
Received: 6 October 2017 / Revised: 23 October 2017 / Accepted: 26 October 2017 / Published: 1 November 2017
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Abstract
We report on the use of different reaction conditions, e.g., temperature, time, and/or concentration of reactants, to gain control over the particle formation of a bioinspired coordination polymer based on copper(II) and adenine, allowing homogeneous particle production from micro- to submicro-, and up
[...] Read more.
We report on the use of different reaction conditions, e.g., temperature, time, and/or concentration of reactants, to gain control over the particle formation of a bioinspired coordination polymer based on copper(II) and adenine, allowing homogeneous particle production from micro- to submicro-, and up to nano-size. Additionally, studies on this reaction carried out in the presence of different surfactants gives rise to the control of the particle size due to the modulation of the electrostatic interactions. Stability of the water suspensions obtained within the time and pH has been evaluated. We have also studied that there is no significant effect of the size reduction in the magnetic properties of the Cu(II)-adenine coordination polymer. Full article
(This article belongs to the Special Issue Coordination Polymer)
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Open AccessArticle Zwitter-Ionic Polymer Applied as Electron Transportation Layer for Improving the Performance of Polymer Solar Cells
Polymers 2017, 9(11), 566; doi:10.3390/polym9110566
Received: 2 October 2017 / Revised: 24 October 2017 / Accepted: 27 October 2017 / Published: 1 November 2017
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Abstract
A zwitter-ionic polymer poly (sulfobetaine methacrylate) (denoted by PSBMA) was employed as an electron transportation layer (ETL) in polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). PSBMA is highly soluble in trifluoroethanol, showing an orthogonal
[...] Read more.
A zwitter-ionic polymer poly (sulfobetaine methacrylate) (denoted by PSBMA) was employed as an electron transportation layer (ETL) in polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). PSBMA is highly soluble in trifluoroethanol, showing an orthogonal solubility to the solvent of the active layer in the preparation of multilayered PSCs. Upon introduction of PSBMA, the short circuit current and as a consequence the power conversion efficiency of the corresponding PSCs are dramatically improved, which can be because of the relatively high polarity of PSBMA compared with the other ETLs. This study demonstrated that zwitter-ionic polymer should be a competitive potential candidate of ETLs in PSCs. Full article
(This article belongs to the Special Issue Polymer Solar Cells)
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Open AccessArticle New Insight into Time-Temperature Correlation for Polymer Relaxations Ranging from Secondary Relaxation to Terminal Flow: Application of a Universal and Developed WLF Equation
Polymers 2017, 9(11), 567; doi:10.3390/polym9110567
Received: 15 October 2017 / Revised: 28 October 2017 / Accepted: 30 October 2017 / Published: 2 November 2017
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Abstract
The three equations involved in the time-temperature superposition (TTS) of a polymer, i.e., Williams–Landel–Ferry (WLF), Vogel–Fulcher–Tammann–Hesse (VFTH) and the Arrhenius equation, were re-examined, and the mathematical equivalence of the WLF form to the Arrhenius form was revealed. As a result, a developed WLF
[...] Read more.
The three equations involved in the time-temperature superposition (TTS) of a polymer, i.e., Williams–Landel–Ferry (WLF), Vogel–Fulcher–Tammann–Hesse (VFTH) and the Arrhenius equation, were re-examined, and the mathematical equivalence of the WLF form to the Arrhenius form was revealed. As a result, a developed WLF (DWLF) equation was established to describe the temperature dependence of relaxation property for the polymer ranging from secondary relaxation to terminal flow, and its necessary criteria for universal application were proposed. TTS results of viscoelastic behavior for different polymers including isotactic polypropylene (iPP), high density polyethylene (HDPE), low density polyethylene (LDPE) and ethylene-propylene rubber (EPR) were well achieved by the DWLF equation at high temperatures. Through investigating the phase-separation behavior of poly(methyl methacrylate)/poly(styrene-co-maleic anhydride) (PMMA/SMA) and iPP/EPR blends, it was found that the DWLF equation can describe the phase separation behavior of the amorphous/amorphous blend well, while the nucleation process leads to a smaller shift factor for the crystalline/amorphous blend in the melting temperature region. Either the TTS of polystyrene (PS) and PMMA or the secondary relaxations of PMMA and polyvinyl chloride (PVC) confirmed that the Arrhenius equation can be valid only in the high temperature region and invalid in the vicinity of glass transition due to the strong dependence of apparent activation energy on temperature; while the DWLF equation can be employed in the whole temperature region including secondary relaxation and from glass transition to terminal relaxation. The theoretical explanation for the universal application of the DWLF equation was also revealed through discussing the influences of free volume and chemical structure on the activation energy of polymer relaxations. Full article
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Open AccessArticle Selective Adsorption of Ag+ on a New Cyanuric-Thiosemicarbazide Chelating Resin with High Capacity from Acid Solutions
Polymers 2017, 9(11), 568; doi:10.3390/polym9110568
Received: 17 September 2017 / Revised: 21 October 2017 / Accepted: 29 October 2017 / Published: 2 November 2017
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Abstract
A new cyanuric-thiosemicarbazid (TSC-CC) chelating resin was synthesized and employed to selectively adsorb Ag+ from acid solutions. The effects of acid concentration, initial concentration of Ag+, contact time and coexisting ions were investigated. The optimal acid concentration was 0.5 mol/L.
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A new cyanuric-thiosemicarbazid (TSC-CC) chelating resin was synthesized and employed to selectively adsorb Ag+ from acid solutions. The effects of acid concentration, initial concentration of Ag+, contact time and coexisting ions were investigated. The optimal acid concentration was 0.5 mol/L. The adsorption capacity of Ag+ reached 872.63 mg/g at acid concentration of 0.5 mol/L. The adsorption isotherm was fitted well with the Langmuir isotherm model and the kinetic data preferably followed the pseudo-second order model. The chelating resin showed a good selectivity for the Ag+ adsorption from acid solutions. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy/energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) were used to study the adsorption mechanism. The chelating and ionic interaction was mainly adsorption mechanism. The adsorbent presents a great potential in selective recovery Ag+ from acid solutions due to the advantage of high adsorption capacity and adapting strongly acidic condition. The recyclability indicated that the (TSC-CC) resin had a good stability and can be recycled as a promising agent for removal of Ag+. Full article
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Open AccessArticle Bio-Based Poly(Ether Imide)s from Isohexide-Derived Isomeric Dianhydrides
Polymers 2017, 9(11), 569; doi:10.3390/polym9110569
Received: 22 September 2017 / Revised: 27 October 2017 / Accepted: 27 October 2017 / Published: 3 November 2017
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Abstract
In this work, four isohexide-derived isomeric dianhydrides were synthesized through a four-step procedure using isohexide and chloro-N-phenylphthalimides as the starting materials. The one-step solution polymerization of these dianhydrides with petroleum- or bio-based diamines enabled the synthesis of poly(ether imide)s (PEIs), which
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In this work, four isohexide-derived isomeric dianhydrides were synthesized through a four-step procedure using isohexide and chloro-N-phenylphthalimides as the starting materials. The one-step solution polymerization of these dianhydrides with petroleum- or bio-based diamines enabled the synthesis of poly(ether imide)s (PEIs), which had viscosities of 0.41 to 2.40 dL∙g−1. The isohexide-derived PEIs were characterized based upon their solubility and their thermal, mechanical, and optical properties. The results showed that most of the isohexide-derived PEIs possessed comparable glass transition temperatures (Tg), tensile strengths, and moduli to petroleum-based PEIs. However, the thermo-oxidative stability of the PEIs was found to be lower than that of the common petroleum-based PEIs. Moreover, the PEIs displayed good optical activity, which originated from their unique chiral isohexide moieties. The isomeric effects of dianhydride monomers on the properties of the resulting PEIs were comparatively studied. The results suggested that the corresponding 4,4′-linked PEIs possessed lower Tg, higher mechanical properties, and higher specific rotations compared to 3,3′-linked polymers. Meanwhile, the polyimides with isomannide residue displayed higher Tg and more specific rotations than the corresponding polymers with isosorbide residue. These results contributed to more restricted rotations of phthalimide segments in 3,3′-linked or isomannide containing polyimides. Full article
(This article belongs to the Special Issue High Performance Polymers)
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Open AccessArticle Effect of Laccase-Mediated Biopolymer Grafting on Kraft Pulp Fibers for Enhancing Paper’s Mechanical Properties
Polymers 2017, 9(11), 570; doi:10.3390/polym9110570
Received: 10 September 2017 / Revised: 27 October 2017 / Accepted: 28 October 2017 / Published: 2 November 2017
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Abstract
High-resistance paper was manufactured by laccase-grafting of carboxymethyl cellulose (CMC) and chitosan (CPX) on Kraft pulp fiber. The reaction was mediated in the presence of laccase by one of the following polyphenols in the presence of air: gallic acid (GA), vanillic acid (VA)
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High-resistance paper was manufactured by laccase-grafting of carboxymethyl cellulose (CMC) and chitosan (CPX) on Kraft pulp fiber. The reaction was mediated in the presence of laccase by one of the following polyphenols in the presence of air: gallic acid (GA), vanillic acid (VA) and catechol (1,2–DHB). Enzyme was added at constant loading (24 kg ton−1), 1% pulp consistency, 0.005% CMC, pH = 6.3 ± 0.5 and 2 mM of mediator. CPX content was assessed at two levels (0% and 0.005%). Treated pulps were analyzed by different mechanical tests (ring crush, mullen, corrugating medium test (CMT) flat crush of corrugating medium test and tension). An improvement in these parameters was obtained by biopolymer coupling and selected mediator. When using GA, three parameters increased more than 40%, while ring crush increased 120%. For the case of VA, properties were enhanced from 74% to 88% when CPX was added. For 1,2–DHB, there was not found a statistically significant difference between the results in the presence of CPX. Scanning electron microscopy, confocal microscopy, FTIR and 13C NMR were used in all papers in order to evaluate grafting. Hence, it was possible to correlate polymerization with an improvement of paper’s mechanical properties. Full article
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Open AccessArticle The Effect of Donor and Nonfullerene Acceptor Inhomogeneous Distribution within the Photoactive Layer on the Performance of Polymer Solar Cells with Different Device Structures
Polymers 2017, 9(11), 571; doi:10.3390/polym9110571
Received: 12 September 2017 / Revised: 26 October 2017 / Accepted: 31 October 2017 / Published: 3 November 2017
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Abstract
Due to the inhomogeneous distribution of donor and acceptor materials within the photoactive layer of bulk heterojunction organic solar cells (OSCs), proper selection of a conventional or an inverted device structure is crucial for effective exciton dissociation and charge transportation. Herein, we investigate
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Due to the inhomogeneous distribution of donor and acceptor materials within the photoactive layer of bulk heterojunction organic solar cells (OSCs), proper selection of a conventional or an inverted device structure is crucial for effective exciton dissociation and charge transportation. Herein, we investigate the donor and acceptor distribution within the non-fullerene photoactive layer based on PBDTTT-ET:IEICO by time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) and scanning Kelvin probe microscopy (SKPM), indicating that more IEICO enriches on the surface of the photoactive layer while PBDTTT-ET distributes homogeneously within the photoactive layer. To further understand the effect of the inhomogeneous component distribution on the photovoltaic performance, both conventional and inverted OSCs were fabricated. As a result, the conventional device shows a power conversion efficiency (PCE) of 8.83% which is 41% higher than that of inverted one (6.26%). Eventually, we employed nickel oxide (NiOx) instead of PEDOT:PSS as anode buffer layer to further enhance the stability and PCE of OSCs with conventional structure, and a promising PCE of 9.12% is achieved. Full article
(This article belongs to the Special Issue Polymer Solar Cells)
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Open AccessArticle Shape Memory Polymers Containing Higher Acrylate Content Display Increased Endothelial Cell Attachment
Polymers 2017, 9(11), 572; doi:10.3390/polym9110572
Received: 6 September 2017 / Revised: 13 October 2017 / Accepted: 31 October 2017 / Published: 3 November 2017
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Abstract
Shape Memory Polymers (SMPs) are smart materials that can recall their shape upon the application of a stimulus, which makes them appealing materials for a variety of applications, especially in biomedical devices. Most prior SMP research has focused on tuning bulk properties; studying
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Shape Memory Polymers (SMPs) are smart materials that can recall their shape upon the application of a stimulus, which makes them appealing materials for a variety of applications, especially in biomedical devices. Most prior SMP research has focused on tuning bulk properties; studying surface effects of SMPs may extend the use of these materials to blood-contacting applications, such as cardiovascular stents, where surfaces that support rapid endothelialization have been correlated to stent success. Here, we evaluate endothelial attachment onto the surfaces of a family of SMPs previously developed in our group that have shown promise for biomedical devices. Nine SMP formulations containing varying amounts of tert-Butyl acrylate (tBA) and Poly(ethylene glycol) dimethacrylate (PEGDMA) were analyzed for endothelial cell attachment. Dynamic mechanical analysis (DMA), contact angle studies, and atomic force microscopy (AFM) were used to verify bulk and surface properties of the SMPs. Human umbilical vein endothelial cell (HUVEC) attachment and viability was verified using fluorescent methods. Endothelial cells preferentially attached to SMPs with higher tBA content, which have rougher, more hydrophobic surfaces. HUVECs also displayed an increased metabolic activity on these high tBA SMPs over the course of the study. This class of SMPs may be promising candidates for next generation blood-contacting devices. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessArticle An Asymmetrical Glycerol Diether Bolalipid with Protonable Phosphodimethylethanolamine Headgroup: The Impact of pH on Aggregation Behavior and Miscibility with DPPC
Polymers 2017, 9(11), 573; doi:10.3390/polym9110573
Received: 28 September 2017 / Revised: 25 October 2017 / Accepted: 31 October 2017 / Published: 3 November 2017
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Abstract
Investigations regarding the self-assembly of (bola)phospholipids in aqueous media are crucial to understand the complex relationship between chemical structure of lipids and the shape and size of their aggregates in water. Here, we introduce a new asymmetrical glycerol diether bolaphospholipid, the compound Me
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Investigations regarding the self-assembly of (bola)phospholipids in aqueous media are crucial to understand the complex relationship between chemical structure of lipids and the shape and size of their aggregates in water. Here, we introduce a new asymmetrical glycerol diether bolaphospholipid, the compound Me2PE-Gly(2C16)C32-OH. This bolalipid contains a long (C32) ω-hydroxy alkyl chain bond to glycerol in the sn-3 position, a C16 alkyl chain at the sn-2 position, and a protonable phosphodimethylethanolamine (Me2PE) headgroup at the sn-1 position of the glycerol. The aggregation behavior of this bolalipid was studied as a function of temperature and pH using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. We show that this bolalipid aggregates into condensed lamellar sheets in acidic milieu and in large sheet-like aggregates at neutral pH-value. By contrast, at a pH-value of 10, where the Me2PE headgroup is only partially protonated, small lipid disks with diameter 50–100 nm were additionally found. Moreover, the miscibility of this asymmetrical bolalipid with the bilayer-forming phosphatidylcholine DPPC was investigated by means of DSC and TEM. The incorporation of bolalipids into phospholipid membranes could result in stabilized liposomes applicable for drug delivery purposes. We show that mixtures of DPPC and Me2PE-Gly(2C16)C32-OH form large lamellar aggregates at pH of 5, 7, and 10. However, closed lipid vesicles (liposomes) with an increased thermal stability were not found. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Ultra-Broadband THz Antireflective Coating with Polymer Composites
Polymers 2017, 9(11), 574; doi:10.3390/polym9110574
Received: 24 September 2017 / Revised: 23 October 2017 / Accepted: 26 October 2017 / Published: 3 November 2017
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Abstract
Achieving an ultra-broadband range is an essential development direction in terahertz techniques; however, a method to cover the full terahertz band by using a highly efficient antireflection (AR) coating that could greatly increase the efficiency of terahertz radiation is still lacking. It is
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Achieving an ultra-broadband range is an essential development direction in terahertz techniques; however, a method to cover the full terahertz band by using a highly efficient antireflection (AR) coating that could greatly increase the efficiency of terahertz radiation is still lacking. It is known that structures possessing a graded-index profile can offer a broadband AR effect, and such structures have been widely used, especially in the visible range. In this paper, first, we tuned the refractive index of a cyclo-olefin polymer (COP) by using a TiO2 dopant, and a polymer–TiO2 composite with a refractive index of 3.1 was achieved. We then fabricated a surface-relief structure with a graded-index profile by using a hot-embossing method. The structure on the silicon substrate can provide an excellent AR effect, but the working band is still limited by its scale of sag and swell. To obtain an ultra-broadband AR effect, we then proposed a flat six-layer structure; a graded-index profile was obtained by casting epoxy–TiO2 composites in the order of a high index to lower indices. With a very well controlled refractive index and thickness of each layer, we achieved an AR effect of <2% in the ultra-broadband of 0.2–20 THz. Full article
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Open AccessArticle Restoration of Impaired Metabolic Energy Balance (ATP Pool) and Tube Formation Potential of Endothelial Cells under “high glucose”, Diabetic Conditions by the Bioinorganic Polymer Polyphosphate
Polymers 2017, 9(11), 575; doi:10.3390/polym9110575
Received: 16 October 2017 / Revised: 1 November 2017 / Accepted: 2 November 2017 / Published: 4 November 2017
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Abstract
Micro-vascularization is a fast, energy-dependent process that is compromised by elevated glucose concentrations such as in diabetes mellitus disease. Here, we studied the effect of the physiological bioinorganic polymer, polyphosphate (polyP), on the reduced ATP content and impaired function of endothelial cells cultivated
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Micro-vascularization is a fast, energy-dependent process that is compromised by elevated glucose concentrations such as in diabetes mellitus disease. Here, we studied the effect of the physiological bioinorganic polymer, polyphosphate (polyP), on the reduced ATP content and impaired function of endothelial cells cultivated under “high glucose” (35 mM diabetes mellitus conditions) concentrations. This high-energy biopolymer has been shown to provide a source of metabolic energy, stored in its phosphoanhydride bonds. We show that exposure of human umbilical vein endothelial cells (HUVEC cells) to “high glucose” levels results in reduced cell viability, increased apoptotic cell death, and a decline in intracellular ATP level. As a consequence, the ability of HUVEC cells to form tube-like structures in the in vitro cell tube formation assay was almost completely abolished under “high glucose” conditions. Those cells were grown onto a physiological collagen scaffold (collagen/basement membrane extract). We demonstrate that these adverse effects of increased glucose levels can be reversed by administration of polyP to almost normal values. Using Na-polyP, complexed in a stoichiometric (molar) ratio to Ca2+ ions and in the physiological concentration range between 30 and 300 µM, an almost complete restoration of the reduced ATP pool of cells exposed to “high glucose” was found, as well as a normalization of the number of apoptotic cells and energy-dependent tube formation. It is concluded that the adverse effects on endothelial cells caused by the metabolic energy imbalance at elevated glucose concentrations can be counterbalanced by polyP, potentially opening new strategies for treatment of the micro-vascular complications in diabetic patients. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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Open AccessArticle A Cationic Smart Copolymer for DNA Binding
Polymers 2017, 9(11), 576; doi:10.3390/polym9110576
Received: 6 October 2017 / Revised: 25 October 2017 / Accepted: 2 November 2017 / Published: 4 November 2017
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Abstract
A new block copolymer with a temperature-responsive block and a cationic block was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization, with good control of its size and composition. The first block is composed by di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethylene
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A new block copolymer with a temperature-responsive block and a cationic block was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization, with good control of its size and composition. The first block is composed by di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA), with the ratio DEGMA/OEGMA being used to choose the volume phase transition temperature of the polymer in water, tunable from ca. 25 to above 90 °C. The second block, of trimethyl-2-methacroyloxyethylammonium chloride (TMEC), is positively charged at physiological pH values and is used for DNA binding. The coacervate complexes between the block copolymer and a model single strand DNA are characterized by fluorescence correlation spectroscopy and fluorescence spectroscopy. The new materials offer good prospects for biomedical application, for example in controlled gene delivery. Full article
(This article belongs to the Special Issue Polymer Characterization)
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Open AccessArticle Dynamics of Dual Scale-Free Polymer Networks
Polymers 2017, 9(11), 577; doi:10.3390/polym9110577
Received: 22 September 2017 / Revised: 29 October 2017 / Accepted: 31 October 2017 / Published: 4 November 2017
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Abstract
We focus on macromolecules which are modeled as sequentially growing dual scale-free networks. The dual networks are built by replacing star-like units of the primal treelike scale-free networks through rings, which are then transformed in a small-world manner up to the complete graphs.
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We focus on macromolecules which are modeled as sequentially growing dual scale-free networks. The dual networks are built by replacing star-like units of the primal treelike scale-free networks through rings, which are then transformed in a small-world manner up to the complete graphs. In this respect, the parameter γ describing the degree distribution in the primal treelike scale-free networks regulates the size of the dual units. The transition towards the networks of complete graphs is controlled by the probability p of adding a link between non-neighboring nodes of the same initial ring. The relaxation dynamics of the polymer networks is studied in the framework of generalized Gaussian structures by using the full eigenvalue spectrum of the Laplacian matrix. The dynamical quantities on which we focus here are the averaged monomer displacement and the mechanical relaxation moduli. For several intermediate values of the parameters’ set ( γ , p ) , we encounter for these dynamical properties regions of constant in-between slope. Full article
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Open AccessArticle Wide Band Gap Polymer Based on Indacenodithiophene and Acenaphthoquinoxaline for Efficient Polymer Solar Cells Application
Polymers 2017, 9(11), 578; doi:10.3390/polym9110578
Received: 9 September 2017 / Revised: 26 October 2017 / Accepted: 31 October 2017 / Published: 7 November 2017
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Abstract
A new wide band gap polymer PIDT-AQx with indacenodithiophene (IDT) as the electron-rich unit and acenaphthoquinoxaline (AQx) as the electron-deficient unit has been designed and synthesized. The optical band gap of PIDT-AQx was 1.81 eV with a HOMO energy level of −5.13 eV.
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A new wide band gap polymer PIDT-AQx with indacenodithiophene (IDT) as the electron-rich unit and acenaphthoquinoxaline (AQx) as the electron-deficient unit has been designed and synthesized. The optical band gap of PIDT-AQx was 1.81 eV with a HOMO energy level of −5.13 eV. Polymer solar cells with the blend of PIDT-AQx/PC71BM as the active layer achieved a power conversion efficiency (PCE) of 4.56%, with an open-circuit voltage (Voc) of 0.84 V, a current density (Jsc) of 9.88 mA cm−2, and a fill factor (FF) of 55% without any solvent additives and pre- or post-treatments. The photovoltaic performance of PIDT-AQx could be slightly improved with a PCE up to 4.78% after thermal annealing due to enhanced Jsc. The results indicate that acenaphthoquinoxaline is a promising building block for developing conjugated polymers for efficient solar cells application. Full article
(This article belongs to the Special Issue Conjugated Polymers 2016)
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Open AccessArticle Development and Characterisation of the Imiquimod Poly(2-(2-methoxyethoxy)ethyl Methacrylate) Hydrogel Dressing for Keloid Therapy
Polymers 2017, 9(11), 579; doi:10.3390/polym9110579
Received: 2 October 2017 / Revised: 30 October 2017 / Accepted: 2 November 2017 / Published: 5 November 2017
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Abstract
The imiquimod-poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogel (poly(MEO2MA) hydrogel) dressing was developed for the keloid therapy application. Four groups of the hydrogels, including the imiquimod-poly(MEO2MA) hydrogel, crosslinked with 0.2 mol %, 0.4 mol %, 0.6 mol %, and 0.8 mol % of
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The imiquimod-poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogel (poly(MEO2MA) hydrogel) dressing was developed for the keloid therapy application. Four groups of the hydrogels, including the imiquimod-poly(MEO2MA) hydrogel, crosslinked with 0.2 mol %, 0.4 mol %, 0.6 mol %, and 0.8 mol % of di(ethylene glycol) dimethacrylate cross-linker (DEGDMA), were synthesised and characterised for fabricating the imiquimod-poly(MEO2MA) hydrogel pad. The lower critical solution temperature (LCST) of the poly(MEO2MA) hydrogel was measured at approximately 28 °C and was used as a trigger to control the imiquimod loading and release. The loaded amounts of the imiquimod in the poly(MEO2MA) hydrogel, crosslinked with 0.2 mol % and 0.8 mol % of DEGDMA, were about 27.4 μg and 14.1 μg per 1 mm3 of the hydrogel, respectively. The imiquimod-release profiles of two samples were characterised in a phosphate buffered saline (PBS) solution at 37 °C and the released imiquimod amount were about 45% and 46% of the total loaded imiquimod. The Cell Counting Kit-8 (CCK-8) assay was utilised to analyse the cell viability of keloid fibroblasts cultured on the samples of imiquimod-poly(MEO2MA) hydrogel, crosslinked with 0.2 mol % and 0.8 mol % of DEGDMA. There was around a 34% decrease of the cell viabilities after 2 days, compared with the pure-poly(MEO2MA) hydrogel samples. Therefore, the developed imiquimod-poly(MEO2MA) hydrogel dressing can affect the proliferation of keloid fibroblasts. It should be possible to utilise the hydrogel dressing for the keloid therapy application. Full article
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Open AccessArticle Matrix Topographical Cue-Mediated Myogenic Differentiation of Human Embryonic Stem Cell Derivatives
Polymers 2017, 9(11), 580; doi:10.3390/polym9110580
Received: 29 September 2017 / Revised: 24 October 2017 / Accepted: 30 October 2017 / Published: 5 November 2017
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Abstract
Biomaterials varying in physical properties, chemical composition and biofunctionalities can be used as powerful tools to regulate skeletal muscle-specific cellular behaviors, including myogenic differentiation of progenitor cells. Biomaterials with defined topographical cues (e.g., patterned substrates) can mediate cellular alignment of progenitor cells and
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Biomaterials varying in physical properties, chemical composition and biofunctionalities can be used as powerful tools to regulate skeletal muscle-specific cellular behaviors, including myogenic differentiation of progenitor cells. Biomaterials with defined topographical cues (e.g., patterned substrates) can mediate cellular alignment of progenitor cells and improve myogenic differentiation. In this study, we employed soft lithography techniques to create substrates with microtopographical cues and used these substrates to study the effect of matrix topographical cues on myogenic differentiation of human embryonic stem cell (hESC)-derived mesodermal progenitor cells expressing platelet-derived growth factor receptor alpha (PDGFRA). Our results show that the majority (>80%) of PDGFRA+ cells on micropatterned polydimethylsiloxane (PDMS) substrates were aligned along the direction of the microgrooves and underwent robust myogenic differentiation compared to those on non-patterned surfaces. Matrix topography-mediated alignment of the mononucleated cells promoted their fusion resulting in mainly (~86%–93%) multinucleated myotube formation. Furthermore, when implanted, the cells on the micropatterned substrates showed enhanced in vivo survival (>5–7 times) and engraftment (>4–6 times) in cardiotoxin-injured tibialis anterior (TA) muscles of NOD/SCID mice compared to cells cultured on corresponding non-patterned substrates. Full article
(This article belongs to the Special Issue Polymer Scaffolds for Biomedical Application)
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Open AccessArticle Propene Polymerization with C1-Symmetric Fluorenyl-Metallocene Catalysts
Polymers 2017, 9(11), 581; doi:10.3390/polym9110581
Received: 11 October 2017 / Revised: 30 October 2017 / Accepted: 31 October 2017 / Published: 6 November 2017
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Abstract
Propene homopolymers have been produced by employing three C1-symmetric metallocene molecules (1, 2 and 3), each having t-butyl substituent(s) on the Cp, on the fluorenyl or on both aromatic moieties activated with methylaluminoxane at different polymerization
[...] Read more.
Propene homopolymers have been produced by employing three C1-symmetric metallocene molecules (1, 2 and 3), each having t-butyl substituent(s) on the Cp, on the fluorenyl or on both aromatic moieties activated with methylaluminoxane at different polymerization temperatures and monomer concentrations. Polymers’ microstructures determined by 13C NMR spectroscopy suggest that the otherwise dominant alternating mechanism governed by the chain migratory insertion is largely replaced by the competing site epimerization mechanism, as a direct result of the imposing steric bulk of the t-butyl substituent on one of the distal positions of the Cp moiety. This phenomenon is more pronounced with 3 when a second t-butyl is present in the same half-space of the molecule making the site epimerization mandatory. The lower activity of catalyst 3 with respect to catalyst 2 is also in line with the necessity for the polymer chain to back-skip (or the site to epimerize) to its original position before the subsequent monomer insertion. Chain end group analyses by 1H NMR spectroscopy have revealed that the formation of vinylidene end groups, either via β-H elimination or as a result of direct chain transfer to the monomer after an ordinary 1,2-insertion is the prevailing chain termination route. A correlation between the relative concentrations of vinylidene end groups of polypropene (PP) polymers produced with each catalyst and the corresponding polypropenes’ molar masses was found, indicating the lower the relative concentrations of vinylidene end groups, the higher the molar masses. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessFeature PaperArticle Stereocomplexation, Thermal and Mechanical Properties of Conetworks Composed of Star-Shaped l-Lactide, d-Lactide and ε-Caprolactone Oligomers Utilizing Sugar Alcohols as Core Molecules
Polymers 2017, 9(11), 582; doi:10.3390/polym9110582
Received: 2 October 2017 / Revised: 30 October 2017 / Accepted: 1 November 2017 / Published: 6 November 2017
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Abstract
It is important to develop tailor-made biodegradable/biocompatible polymer networks usable for biomaterials whose thermal and mechanical properties are easily controlled by changing the composition. We synthesized sugar-alcohol-based polymer networks (SPN-mscLAO/3CLO, m = 4, 5 or 6) by the crosslinking reactions of
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It is important to develop tailor-made biodegradable/biocompatible polymer networks usable for biomaterials whose thermal and mechanical properties are easily controlled by changing the composition. We synthesized sugar-alcohol-based polymer networks (SPN-mscLAO/3CLO, m = 4, 5 or 6) by the crosslinking reactions of erythritol, xylitol or sorbitol-based m-armed star-shaped l-lactide and d-lactide oligomers (HmSLLAO and HmSDLAO), a glycerol-based 3-armed star-shaped ε-caprolactone oligomer (H3SCLO) and hexamethylene diisocyanate (HDI) at the weight ratios of HmSLLAO/HmSDLAO = 1/1 and (HmSLLAO + HmSDLAO)/H3CLO = 100/0, 75/25, 50/50, 25/75 or 0/100). The influence of the arm number on the crystallization behavior, thermal and mechanical properties of SPN-mscLAO/3CLOs were systematically investigated by comparing with those of sugar-alcohol-based homochiral polymer network (SPN-mLLAO, m = 4, 5 or 6) prepared by the reaction of HmSLLAO and HDI. Stereocomplex (sc) crystallites are dominantly formed for SPN-mscLAO/3CLOs 100/0–25/75, whereas SPN-mLLAOs were amorphous. The higher order of melting temperature of sc-crystals for SPN-mscLAO/3CLOs 100/0–25/75 was m = 5 > m = 6 > m = 4. The sc-crystallinities of SPN-4scLAO/3CLOs 100/0–50/50 were significantly lower than those of SPN-mscLAO/3CLOs 100/0–50/50 (m = 5 and 6). The larger order of the sc-spherulite size at crystallization temperature of 110 °C was m = 5 > m = 6 > m = 4 for SPN-mscLAO/3CLO 100/0. The size and number of sc-spherulites decreased with increasing crystallization temperature over the range of 110–140 °C and with increasing CLO fraction. Among all the networks, SPN-5scLAO/3CLOs 75/25 and 50/50 exhibited the highest and second highest tensile toughnesses (21.4 and 20.3 MJ·m−3), respectively. Full article
(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)
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Open AccessCommunication Reducing Water Sensitivity of Chitosan Biocomposite Films Using Gliadin Particles Made by In Situ Method
Polymers 2017, 9(11), 583; doi:10.3390/polym9110583
Received: 8 October 2017 / Revised: 3 November 2017 / Accepted: 4 November 2017 / Published: 6 November 2017
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Abstract
In order to sustain rapid expansion in the field of biocomposites, it is necessary to develop novel fillers that are biodegradable, and easy to disperse and obtain. In this work, gliadin particles (GPs) fabricated through an in situ method have been reported as
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In order to sustain rapid expansion in the field of biocomposites, it is necessary to develop novel fillers that are biodegradable, and easy to disperse and obtain. In this work, gliadin particles (GPs) fabricated through an in situ method have been reported as fillers for creating chitosan (CS)-based biocomposite films. In general, the particles tend to agglomerate in the polymer matrix at high loading (approximately >10%) in the biopolymer/particles composites prepared by the traditional solution-blending method. However, the micrographs of biocomposites confirmed that the GPs are well dispersed in the CS matrix in all CS/GPs composites even at a high loading of 30% in this study. It was found that the GPs could improve the mechanical properties of the biocomposites. In addition, the results of moisture uptake and solubility in water of biocomposites showed that water resistance of biocomposites was enhanced by the introduction of GPs. These results suggested that GPs fabricated through an in situ method could be a good candidate for use in biopolymer-based composites. Full article
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Open AccessArticle 3D Biofabrication of Thermoplastic Polyurethane (TPU)/Poly-l-lactic Acid (PLLA) Electrospun Nanofibers Containing Maghemite (γ-Fe2O3) for Tissue Engineering Aortic Heart Valve
Polymers 2017, 9(11), 584; doi:10.3390/polym9110584
Received: 21 September 2017 / Revised: 24 October 2017 / Accepted: 3 November 2017 / Published: 6 November 2017
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Abstract
Valvular dysfunction as the prominent reason of heart failure may causes morbidity and mortality around the world. The inability of human body to regenerate the defected heart valves necessitates the development of the artificial prosthesis to be replaced. Besides, the lack of capacity
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Valvular dysfunction as the prominent reason of heart failure may causes morbidity and mortality around the world. The inability of human body to regenerate the defected heart valves necessitates the development of the artificial prosthesis to be replaced. Besides, the lack of capacity to grow, repair or remodel of an artificial valves and biological difficulty such as infection or inflammation make the development of tissue engineering heart valve (TEHV) concept. This research presented the use of compound of poly-l-lactic acid (PLLA), thermoplastic polyurethane (TPU) and maghemite nanoparticle (γ-Fe2O3) as the potential biomaterials to develop three-dimensional (3D) aortic heart valve scaffold. Electrospinning was used for fabricating the 3D scaffold. The steepest ascent followed by the response surface methodology was used to optimize the electrospinning parameters involved in terms of elastic modulus. The structural and porosity properties of fabricated scaffold were characterized using FE-SEM and liquid displacement technique, respectively. The 3D scaffold was then seeded with aortic smooth muscle cells (AOSMCs) and biological behavior in terms of cell attachment and proliferation during 34 days of incubation was characterized using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and confocal laser microscopy. Furthermore, the mechanical properties in terms of elastic modulus and stiffness were investigated after cell seeding through macro-indentation test. The analysis indicated the formation of ultrafine quality of nanofibers with diameter distribution of 178 ± 45 nm and 90.72% porosity. In terms of cell proliferation, the results exhibited desirable proliferation (109.32 ± 3.22% compared to the control) of cells over the 3D scaffold in 34 days of incubation. The elastic modulus and stiffness index after cell seeding were founded to be 22.78 ± 2.12 MPa and 1490.9 ± 12 Nmm2, respectively. Overall, the fabricated 3D scaffold exhibits desirable structural, biological and mechanical properties and has the potential to be used in vivo. Full article
(This article belongs to the Special Issue Electrospinning of Nanofibres)
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Open AccessArticle Mechanical Properties Distribution within Polypropylene Injection Molded Samples: Effect of Mold Temperature under Uneven Thermal Conditions
Polymers 2017, 9(11), 585; doi:10.3390/polym9110585
Received: 13 October 2017 / Revised: 1 November 2017 / Accepted: 3 November 2017 / Published: 7 November 2017
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Abstract
The quality of the polymer parts produced by injection molding is strongly affected by the processing conditions. Uncontrolled deviations from the proper process parameters could significantly affect both internal structure and final material properties. In this work, to mimic an uneven temperature field,
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The quality of the polymer parts produced by injection molding is strongly affected by the processing conditions. Uncontrolled deviations from the proper process parameters could significantly affect both internal structure and final material properties. In this work, to mimic an uneven temperature field, a strong asymmetric heating is applied during the production of injection-molded polypropylene samples. The morphology of the samples is characterized by optical and atomic force microscopy (AFM), whereas the distribution of mechanical modulus at different scales is obtained by Indentation and HarmoniX AFM tests. Results clearly show that the temperature differences between the two mold surfaces significantly affect the morphology distributions of the molded parts. This is due to both the uneven temperature field evolutions and to the asymmetric flow field. The final mechanical property distributions are determined by competition between the local molecular stretch and the local structuring achieved during solidification. The cooling rate changes affect internal structures in terms of relaxation/reorganization levels and give rise to an asymmetric distribution of mechanical properties. Full article
(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers)
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Open AccessArticle Large-Scale and Flexible Self-Powered Triboelectric Tactile Sensing Array for Sensitive Robot Skin
Polymers 2017, 9(11), 586; doi:10.3390/polym9110586
Received: 11 September 2017 / Revised: 31 October 2017 / Accepted: 2 November 2017 / Published: 7 November 2017
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Abstract
Advances in flexible and multifunctional electronic devices have enabled the realization of sophisticated skin for robotics applications. In this paper, a large-scale, flexible and self-powered tactile sensing array (TSA) for sensitive robot skin is demonstrated based on the triboelectric effect. The device, with
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Advances in flexible and multifunctional electronic devices have enabled the realization of sophisticated skin for robotics applications. In this paper, a large-scale, flexible and self-powered tactile sensing array (TSA) for sensitive robot skin is demonstrated based on the triboelectric effect. The device, with 4 × 4 sensing units, was composed of a top triboelectric polyethylene terephthalate (PET) layer, a bottom triboelectric copper (Cu) layer and a bottom PET substrate. A low-cost roll-to-roll ultraviolet embossing fabrication process was induced to pattern the large-scale top PET film with microstructures for high-output performance. The working mechanism and output performance of the triboelectric TSA were demonstrated and characterized, exhibiting good stability and high sensitivity. By integrating a tactile feedback system, the large-scale TSA, acting as intelligent skin for an industrial robot, was able to realize emergency avoidance and safety stop for various unknown obstacles under various working conditions. The system also has good real-time performance. By using a large-scale roll-to-roll fabrication method, this work pushes forward a significant step to self-powered triboelectric TSA and its potential applications in intelligent robot skin. Full article
(This article belongs to the Special Issue Wearable Sensor)
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Open AccessArticle Interfacial Properties of Bamboo Fiber-Reinforced High-Density Polyethylene Composites by Different Methods for Adding Nano Calcium Carbonate
Polymers 2017, 9(11), 587; doi:10.3390/polym9110587
Received: 11 October 2017 / Revised: 1 November 2017 / Accepted: 1 November 2017 / Published: 7 November 2017
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Abstract
The focus of this study was to observe the effect of nano calcium carbonate (CaCO3) modification methods on bamboo fiber (BF) used in BF-reinforced high-density polyethylene (HDPE) composites manufactured by extrusion molding. Two methods were used to introduce the nano CaCO
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The focus of this study was to observe the effect of nano calcium carbonate (CaCO3) modification methods on bamboo fiber (BF) used in BF-reinforced high-density polyethylene (HDPE) composites manufactured by extrusion molding. Two methods were used to introduce the nano CaCO3 into the BF for modification; the first was blending modification (BM) and the second was impregnation modification (IM). In order to determine the effects of the modification methods, the water absorption, surface free energy and interfacial properties of the unmodified composites were compared to those of the composites made from the two modification methods. The results revealed that the percentage increase in the weight of the composite treated by nano CaCO3 decreased and that of the IMBF/HDPE composite was the lowest over the seven months of time. The results obtained by the acid-base model according to the Lewis and Owens-Wendt- Rabel-Kaelble (OWRK) equations indicated that the surface energy of the composites was between 40 and 50 mJ/m2. When compared to the control sample, the maximum storage modulus (E′max) of the BMBF/HDPE and IMBF/HDPE composites increased 1.43- and 1.53-fold, respectively. The values of the phase-to-phase interaction parameter B and the k value of the modified composites were higher than those of the unmodified composites, while the apparent activation energy Ea and interface parameter A were lower in the modified composites. It can be concluded that nano CaCO3 had an effect on the interfacial properties of BF-reinforced HDPE composites, and the interface bonding between IMBF and HDPE was greatest among the composites. Full article
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Open AccessArticle Extraction and Characterization of Cellulose Nanocrystals from Tea Leaf Waste Fibers
Polymers 2017, 9(11), 588; doi:10.3390/polym9110588
Received: 13 October 2017 / Revised: 1 November 2017 / Accepted: 2 November 2017 / Published: 7 November 2017
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Abstract
The aim was to explore the utilization of tea leaf waste fibers (TLWF) as a source for the production of cellulose nanocrystals (CNC). TLWF was first treated with alkaline, followed by bleaching before being hydrolyzed with concentrated sulfuric acid. The materials attained after
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The aim was to explore the utilization of tea leaf waste fibers (TLWF) as a source for the production of cellulose nanocrystals (CNC). TLWF was first treated with alkaline, followed by bleaching before being hydrolyzed with concentrated sulfuric acid. The materials attained after each step of chemical treatments were characterized and their chemical compositions were studied. The structure analysis was examined by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). From FTIR analysis, two peaks at 1716 and 1207 cm−1—which represent C=O stretching and C–O stretching, respectively—disappeared in the spectra after the alkaline and bleaching treatments indicated that hemicellulose and lignin were almost entirely discarded from the fiber. The surface morphology of TLWF before and after chemical treatments was investigated by scanning electron microscopy (SEM) while the dimension of CNC was determined by transmission electron microscopy (TEM). The extraction of CNC increased the surface roughness and the crystallinity index of fiber from 41.5% to 83.1%. Morphological characterization from TEM revealed the appearance of needle-like shaped CNCs with average diameter of 7.97 nm. The promising results from all the analyses justify TLWF as a principal source of natural materials which can produce CNC. Full article
(This article belongs to the Special Issue Polysaccharides)
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Open AccessArticle Blood Compatibility of ZrO2 Particle Reinforced PEEK Coatings on Ti6Al4V Substrates
Polymers 2017, 9(11), 589; doi:10.3390/polym9110589
Received: 1 October 2017 / Revised: 30 October 2017 / Accepted: 6 November 2017 / Published: 10 November 2017
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Abstract
Titanium (Ti) and its alloys are widely used in biomedical devices. As biomaterials, the blood compatibility of Ti and its alloys is important and needs to be further improved to provide better functionality. In this work, we studied the suitability of zirconia (ZrO
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Titanium (Ti) and its alloys are widely used in biomedical devices. As biomaterials, the blood compatibility of Ti and its alloys is important and needs to be further improved to provide better functionality. In this work, we studied the suitability of zirconia (ZrO2) particle reinforced poly-ether-ether-ketone (PEEK) coatings on Ti6Al4V substrates for blood-contacting implants. The wettability, surface roughness and elastic modulus of the coatings were examined. Blood compatibility tests were conducted by erythrocytes observation, hemolysis assay and clotting time of recalcified human plasma, to find out correlations between the microstructure of the ZrO2-filled PEEK composite coatings and their blood compatibilities. The results suggested that adding ZrO2 nanoparticles increased the surface roughness and improved the wettability and Derjaguin-Muller-Toporov (DMT) elastic modulus of PEEK coating. The PEEK composite matrix coated Ti6Al4V specimens did not cause any aggregation of erythrocytes, showing morphological normal shapes. The hemolysis rate (HR) values of the tested specimens were much less than 5% according to ISO 10993-4 standard. The values of plasma recalcification time (PRT) of the tested specimens varied with the increasing amount of ZrO2 nanoparticles. Based on the results obtained, 10 wt % ZrO2 particle reinforced PEEK coating has demonstrated an optimum blood compatibility, and can be considered as a candidate to improve the performance of existing PEEK based coatings on titanium substrates. Full article
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Open AccessArticle Bimetallic Catalytic Systems Based on Sb, Ge and Ti for the Synthesis of Poly(ethylene terephthalate-co-isosorbide terephthalate)
Polymers 2017, 9(11), 590; doi:10.3390/polym9110590
Received: 10 October 2017 / Revised: 27 October 2017 / Accepted: 6 November 2017 / Published: 9 November 2017
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Abstract
The insertion of rigid monomers such as isosorbide into poly(ethylene terephthalate) (PET) allows for the access of polymers with improved properties, notably in terms of thermal stability. This biobased monomer is however poorly reactive, and harsh reaction conditions lead to color concerns regarding
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The insertion of rigid monomers such as isosorbide into poly(ethylene terephthalate) (PET) allows for the access of polymers with improved properties, notably in terms of thermal stability. This biobased monomer is however poorly reactive, and harsh reaction conditions lead to color concerns regarding the resulting polymer. This has motivated the development of catalytic systems enabling an increase of the reaction rate and a good coloration. In this study, we have assessed bimetallic catalytic systems based on the main metals used for PET catalysis, i.e., antimony, germanium and titanium, for the synthesis of poly(ethylene terephthalate-co-isosorbide terephthalate) (PEIT). The Sb2O3/Ti(OiPr)4 combination leads to a high reaction rate while maintaining an acceptable coloration. On the other hand, combining Sb2O3 with GeO2 affords the formation of poly(ethylene terephthalate-co-isosorbide terephthalate) without coloration concerns and a reaction rate higher than that observed using the single metal catalysts. Molecular weights and microstructure including diethyleneglycol (DEG) and isosorbide contents are also discussed, together with the thermal properties of the resulting PEIT. The GeO2/Ti(OiPr)4 is also assessed, and leads to average performances. Full article
(This article belongs to the Special Issue Biodegradable and Biobased Polyesters)
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Open AccessArticle Effect of MAH-g-PLA on the Properties of Wood Fiber/Polylactic Acid Composites
Polymers 2017, 9(11), 591; doi:10.3390/polym9110591
Received: 7 October 2017 / Revised: 7 November 2017 / Accepted: 7 November 2017 / Published: 9 November 2017
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Abstract
Maleic anhydride (MAH) was used as the grafting monomer, which was prepared by melt grafting reaction in the twin screw extruder with dicumyl peroxide (DCP) as the initiator, polylactic acid grafted with maleic anhydride (MAH-g-PLA) was successfully prepared as the interface compatibilizer. The
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Maleic anhydride (MAH) was used as the grafting monomer, which was prepared by melt grafting reaction in the twin screw extruder with dicumyl peroxide (DCP) as the initiator, polylactic acid grafted with maleic anhydride (MAH-g-PLA) was successfully prepared as the interface compatibilizer. The PLA/Wood fiber/MAH-g-PLA composites were prepared by melt blending and injection molding with different proportions of compatibilizer added, within which PLA was for the matrix phase and wood fiber was for the reinforcing phase. The crystallinity, microstructure, thermal stability and dynamic thermomechanical property of the composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), thermo gravimetric analyzer (TGA) and dynamic mechanical thermal analysis (DMA). Furthermore, the mechanical and water absorption properties of the composites were also characterized. Results showed that the tensile strength and flexural strength of the composites attained the highest at 30% MAH-g-PLA added, where the crystallinity of the composites also showed the highest value. DMA results showed that the addition of MAH-g-PLA interfacial compatibilizer increased the loss modulus of the composites and improved the toughness. Scanning electron microscopy (SEM) showed that when the MAH-g-PLA was used, wood fiber is well dispersed in the PLA matrix phase, and that the interfacial compatibility between the matrix and the enhanced phase was improved. Therefore, the addition of MAH-g-PLA could improve the interfacial compatibility of PLA/Wood fiber composites and improve the mechanical properties of the composites. Full article
(This article belongs to the collection Polymeric Adhesives)
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Open AccessArticle Enhancing Stereocomplexation Ability of Polylactide by Coalescing from Its Inclusion Complex with Urea
Polymers 2017, 9(11), 592; doi:10.3390/polym9110592
Received: 12 October 2017 / Revised: 4 November 2017 / Accepted: 9 November 2017 / Published: 9 November 2017
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Abstract
In this study, polylactide/urea complexes were successfully prepared by the electrospinning method, then the host urea component was removed to obtain a coalesced poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA) blend. The crystallization behavior of the coalesced PLLA/PDLA blend (c-PLLA/PDLA) was studied by a differential scanning calorimeter
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In this study, polylactide/urea complexes were successfully prepared by the electrospinning method, then the host urea component was removed to obtain a coalesced poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA) blend. The crystallization behavior of the coalesced PLLA/PDLA blend (c-PLLA/PDLA) was studied by a differential scanning calorimeter (DSC) and Fourier transform infrared (FTIR) spectroscopy. The c-PLLA/PDLA was found to show better crystallization ability than normal PLLA/PDLA blend (r-PLLA/PDLA). More interestingly, the c-PLLA/PDLA effectively and solely crystallized into stereocomplex crystals during the non-isothermal melt-crystallization process, and the reason was attributed to the equally-distributing state of PLLA and PDLA chains in the PLLA/PDLA/urea complex, which led to good interconnection between PLLA and PDLA chains when the urea frameworks were instantly removed. Full article
(This article belongs to the Special Issue Host-Guest Polymer Complexes)
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Open AccessArticle Fully Biodegradable Biocomposites with High Chicken Feather Content
Polymers 2017, 9(11), 593; doi:10.3390/polym9110593
Received: 16 October 2017 / Revised: 6 November 2017 / Accepted: 8 November 2017 / Published: 9 November 2017
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Abstract
The aim of this work was to develop new biodegradable polymeric materials with high loadings of chicken feather (CF). In this study, the effect of CF concentration and the type of biodegradable matrix on the physical, mechanical and thermal properties of the biocomposites
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The aim of this work was to develop new biodegradable polymeric materials with high loadings of chicken feather (CF). In this study, the effect of CF concentration and the type of biodegradable matrix on the physical, mechanical and thermal properties of the biocomposites was investigated. The selected biopolymers were polylactic acid (PLA), polybutyrate adipate terephthalate (PBAT) and a PLA/thermoplastic copolyester blend. The studied biocomposites were manufactured with a torque rheometer having a CF content of 50 and 60 wt %. Due to the low tensile strength of CFs, the resulting materials were penalized in terms of mechanical properties. However, high-loading CF biocomposites resulted in lightweight and thermal-insulating materials when compared with neat bioplastics. Additionally, the adhesion between CFs and the PLA matrix was also investigated and a significant improvement of the wettability of the feathers was obtained with the alkali treatment of the CFs and the addition of a plasticizer like polyethylene glycol (PEG). Considering all the properties, these 100% fully biodegradable biocomposites could be adequate for panel components, flooring or building materials as an alternative to wood–plastic composites, contributing to the valorisation of chicken feather waste as a renewable material. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle The Study of Thermal, Mechanical and Shape Memory Properties of Chopped Carbon Fiber-Reinforced TPI Shape Memory Polymer Composites
Polymers 2017, 9(11), 594; doi:10.3390/polym9110594
Received: 13 October 2017 / Revised: 4 November 2017 / Accepted: 6 November 2017 / Published: 10 November 2017
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Abstract
Trans-l,4-polyisoprene (TPI) shape memory polymer composites with different chopped carbon fiber mass fractions were prepared to study the effects of different chopped carbon fiber mass fractions and temperatures on the TPI shape memory polymer composites in this paper. While guaranteeing the shape memory
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Trans-l,4-polyisoprene (TPI) shape memory polymer composites with different chopped carbon fiber mass fractions were prepared to study the effects of different chopped carbon fiber mass fractions and temperatures on the TPI shape memory polymer composites in this paper. While guaranteeing the shape memory effect of TPI shape memory polymers, the carbon fiber fillers also significantly enhanced the mechanical properties of the polymers. The thermodynamic properties and shape memory properties of TPI shape memory polymers were studied by a differential scanning calorimeter (DSC) test, dynamic mechanical analysis (DMA) test, thermal conductivity test, static tensile test, mechanical cycle test, thermodynamic cycling test and shape memory test. Furthermore, the tensile fracture interface of TPI shape memory polymer composites was analyzed by scanning electron microscopy. The experimental results show that when the chopped carbon mass fraction fiber is 8%, TPI shape memory polymers have good shape memory properties and the best mechanical properties. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessArticle Novel Isocyanate-Modified Carrageenan Polymer Materials: Preparation, Characterization and Application Adsorbent Materials of Pharmaceuticals
Polymers 2017, 9(11), 595; doi:10.3390/polym9110595
Received: 27 September 2017 / Revised: 4 November 2017 / Accepted: 6 November 2017 / Published: 10 November 2017
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Abstract
The present study focused on the synthesis and application of novel isocyanate-modified carrageenan polymers as sorbent materials for pre-concentration and removal of diclofenac (DCF) and carbamazepine (CBZ) in different aqueous matrices (surface waters and wastewaters). The polymer materials were characterized using Fourier transform
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The present study focused on the synthesis and application of novel isocyanate-modified carrageenan polymers as sorbent materials for pre-concentration and removal of diclofenac (DCF) and carbamazepine (CBZ) in different aqueous matrices (surface waters and wastewaters). The polymer materials were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). The effects on the adsorption behavior were studied, and the equilibrium data were fitted by the Langmuir and Freundlich models. The maximum adsorption capacity (Qmax) was determined by Langmuir–Freundlich model and was ranged for iota-carrageenan (iCAR) from 7.44 to 8.51 mg/g for CBZ and 23.41 to 35.78 mg/g for DCF and for kappa-carrageenan (kCAR) from 7.07 to 13.78 mg/g for CBZ and 22.66 to 49.29 mg/g for DCF. In the next step, dispersive solid phase extraction (D-SPE) methodology followed by liquid desorption and liquid chromatography mass spectrometry (LC/MS) has been developed and validated. The factors, which affect the performance of D-SPE, were investigated. Then, the optimization of extraction time, sorbent mass and eluent’s volume was carried out using a central composite design (CCD) and response surface methodology (RSM). Under the optimized conditions, good linear relationships have been achieved with the correlation coefficient (R2) varying from 0.9901 to 0.995. The limits of detections (LODs) and limits of quantifications (LOQs) ranged 0.042–0.090 μg/L and 0.137–0.298 μg/L, respectively. The results of the recoveries were 70–108% for both analytes, while the precisions were 2.8–17.5% were obtained, which indicated that the method was suitable for the analysis of both compounds in aqueous matrices. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle Flexible Ultrahigh-Temperature Polymer-Based Dielectrics with High Permittivity for Film Capacitor Applications
Polymers 2017, 9(11), 596; doi:10.3390/polym9110596
Received: 24 August 2017 / Revised: 22 September 2017 / Accepted: 2 November 2017 / Published: 10 November 2017
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Abstract
In this report, flexible cross-linked polyarylene ether nitrile/functionalized barium titanate(CPEN/F-BaTiO3) dielectrics films with high permittivitywere prepared and characterized. The effects of both the F-BaTiO3 and matrix curing on the mechanical, thermal and dielectric properties of the CPEN/F-BaTiO3 dielectric films
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In this report, flexible cross-linked polyarylene ether nitrile/functionalized barium titanate(CPEN/F-BaTiO3) dielectrics films with high permittivitywere prepared and characterized. The effects of both the F-BaTiO3 and matrix curing on the mechanical, thermal and dielectric properties of the CPEN/F-BaTiO3 dielectric films were investigated in detail. Compared to pristine BaTiO3, the surface modified BaTiO3 particles effectively improved their dispersibility and interfacial adhesion in the polymer matrix. Moreover, the introduction of F-BaTiO3 particles enhanced dielectric properties of the composites, with a relatively high permittivity of 15.2 and a quite low loss tangent of 0.022 (1 kHz) when particle contents of 40 wt % were utilized. In addition, the cyano (–CN) groups of functional layer also can serve as potential sites for cross-linking with polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) matrix and make it transform from thermoplastic to thermosetting. Comparing with the pure PEN-ph film, the latter results indicated that the formation of cross-linked network in the polymer-based system resulted in increased tensile strength by ~67%, improved glass transition temperature (Tg) by ~190 °C. More importantly, the CPEN/F-BaTiO3 composite films filled with 30 wt % F-BaTiO3 particles showed greater energy density by nearly 190% when compared to pure CPEN film. These findings enable broader applications of PEN-based composites in high-performance electronics and energy storage devices materials used at high temperature. Full article
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Open AccessArticle Synthesis and Characterization of Cellulose Nanofibril-Reinforced Polyurethane Foam
Polymers 2017, 9(11), 597; doi:10.3390/polym9110597
Received: 11 October 2017 / Revised: 31 October 2017 / Accepted: 8 November 2017 / Published: 10 November 2017
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Abstract
In this study, traditional polyol was partially replaced with green, environmentally friendly cellulose nanofibrils (CNF). The effects of CNF on the performance of CNF-reinforced polyurethane foam nanocomposites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric
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In this study, traditional polyol was partially replaced with green, environmentally friendly cellulose nanofibrils (CNF). The effects of CNF on the performance of CNF-reinforced polyurethane foam nanocomposites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and a compression test. The results showed that the introduction of CNF into the polyurethane matrix not only created stronger urethane bonding between the hydroxyl groups in the cellulose chain and isocyanate groups in polymethylene polyphenylisocyanate, but also developed an additional filler–matrix interaction between CNF and polyurethane. With the increase of the CNF replacement ratio, a higher glass transition temperature was obtained, and a higher amount of char residue was generated. In addition, an increase of up to 18-fold in compressive strength was achieved for CNF-PUF (polyurethane foam) nanocomposites with a 40% CNF replacement ratio. CNF has proved to be a promising substitute for traditional polyols in the preparation of polyurethane foams. This study provides an interesting method to synthesize highly green bio-oriented polyurethane foams. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle Surface Modification of Cardiovascular Stent Material 316L SS with Estradiol-Loaded Poly (trimethylene carbonate) Film for Better Biocompatibility
Polymers 2017, 9(11), 598; doi:10.3390/polym9110598
Received: 11 September 2017 / Revised: 8 November 2017 / Accepted: 9 November 2017 / Published: 10 November 2017
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Abstract
A delay in the endothelialization process represents a bottleneck in the application of a drug-eluting stent (DES) during cardiovascular interventional therapy, which may lead to a high risk of late restenosis. In this study, we used a novel active drug, estradiol, which may
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A delay in the endothelialization process represents a bottleneck in the application of a drug-eluting stent (DES) during cardiovascular interventional therapy, which may lead to a high risk of late restenosis. In this study, we used a novel active drug, estradiol, which may contribute to surface endothelialization of a DES, and prepared an estradiol-loaded poly (trimethylene carbonate) film (PTMC-E5) on the surface of the DES material, 316L stainless steel (316L SS), in order to evaluate its function in improving surface endothelialization. All the in vitro and in vivo experiments indicated that the PTMC-E5 film significantly improved surface hemocompatibility and anti-hyperplasia, anti-inflammation and pro-endothelialization properties. This novel drug-delivery system may provide a breakthrough for the surface endothelialization of cardiovascular DES. Full article
(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)
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Open AccessArticle Effect of Glycerol Pretreatment on Levoglucosan Production from Corncobs by Fast Pyrolysis
Polymers 2017, 9(11), 599; doi:10.3390/polym9110599
Received: 30 September 2017 / Revised: 5 November 2017 / Accepted: 7 November 2017 / Published: 10 November 2017
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Abstract
In this manuscript, glycerol was used in corncobs’ pretreatment to promote levoglucosan production by fast pyrolysis first and then was further utilized as raw material for chemicals production by microbial fermentation. The effects of glycerol pretreatment temperatures (220–240 °C), time (0.5–3 h) and
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In this manuscript, glycerol was used in corncobs’ pretreatment to promote levoglucosan production by fast pyrolysis first and then was further utilized as raw material for chemicals production by microbial fermentation. The effects of glycerol pretreatment temperatures (220–240 °C), time (0.5–3 h) and solid-to-liquid ratios (5–20%) were investigated. Due to the accumulation of crystalline cellulose and the removal of minerals, the levoglucosan yield was as high as 35.8% from corncobs pretreated by glycerol at 240 for 3 h with a 5% solid-to-liquid ratio, which was obviously higher than that of the control (2.2%). After glycerol pretreatment, the fermentability of the recovered glycerol remaining in the liquid stream from glycerol pretreatment was evaluated by Klebsiella pneumoniae. The results showed that the recovered glycerol had no inhibitory effect on the growth and metabolism of the microbe, which was a promising substrate for fermentation. The value-added applications of glycerol could reduce the cost of biomass pretreatment. Correspondingly, this manuscript offers a green, sustainable, efficient and economic strategy for an integrated biorefinery process. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle Hygral Behavior of Superabsorbent Polymers with Various Particle Sizes and Cross-Linking Densities
Polymers 2017, 9(11), 600; doi:10.3390/polym9110600
Received: 5 October 2017 / Revised: 5 November 2017 / Accepted: 7 November 2017 / Published: 10 November 2017
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Abstract
This study focuses on investigating the effects of particle size and cross-linking density on the hygral behavior of superabsorbent polymers (SAPs), which are increasingly used as an internal curing material for high-performance concrete. Four SAPs with different mean particle diameters and cross-linking densities
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This study focuses on investigating the effects of particle size and cross-linking density on the hygral behavior of superabsorbent polymers (SAPs), which are increasingly used as an internal curing material for high-performance concrete. Four SAPs with different mean particle diameters and cross-linking densities were tested under controlled wetting and drying conditions to measure free absorption and desorption kinetics. Absorption capacities of SAPs under actual mixing conditions were additionally measured and verified by means of mortar flow and semi-adiabatic hydration heat measurements. In addition, the effects of SAP type and dosage (i.e., 0.2, 0.4, and 0.6% by mass of cement) on the mechanical properties of hardened mortar were assessed. The results indicated that: (1) the absorption capacity increased with decreased cross-linking density and increased particle size under both load-free and mixing conditions; and (2) the greater the cross-linking density and the lower the particle size, the shorter the desorption time. It was also confirmed that while the early-age mechanical properties were more related with the gel strength of swollen SAP, the later-age mechanical properties were more affected by the water retention capacity and spatial distribution of SAP in the matrix. Full article
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Open AccessArticle Nitric Oxide Releasing Polymeric Coatings for the Prevention of Biofilm Formation
Polymers 2017, 9(11), 601; doi:10.3390/polym9110601
Received: 31 August 2017 / Revised: 30 October 2017 / Accepted: 8 November 2017 / Published: 11 November 2017
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Abstract
The ability of nitric oxide (NO)-releasing polymer coatings to prevent biofilm formation is described. NO-releasing coatings on (poly(ethylene terephthalate) (PET) and silicone elastomer (SE)) were fabricated using aminosilane precursors. Pristine PET and SE were oxygen plasma treated, followed by immobilisation of two aminosilane
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The ability of nitric oxide (NO)-releasing polymer coatings to prevent biofilm formation is described. NO-releasing coatings on (poly(ethylene terephthalate) (PET) and silicone elastomer (SE)) were fabricated using aminosilane precursors. Pristine PET and SE were oxygen plasma treated, followed by immobilisation of two aminosilane molecules: N-(3-(trimethoxysilyl)propyl)diethylenetriamine (DET3) and N-(3-trimethoxysilyl)propyl)aniline (PTMSPA). N-diazeniumdiolate nitric oxide donors were formed at the secondary amine sites on the aminosilane molecules producing NO-releasing polymeric coatings. The NO payload and release were controlled by the aminosilane precursor, as DET3 has two secondary amine sites and PTMSPA only one. The antibacterial efficacy of these coatings was tested using a clinical isolate of Pseudomonas aeruginosa (PA14). All NO-releasing coatings in this study were shown to significantly reduce P. aeruginosa adhesion over 24 h with the efficacy being a function of the aminosilane modification and the underlying substrate. These NO-releasing polymers demonstrate the potential and utility of this facile coating technique for preventing biofilms for indwelling medical devices. Full article
(This article belongs to the Special Issue Advance of Polymers Applied to Biomedical Applications: Biointerface)
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Open AccessArticle The Effects of Using Sodium Alginate Hydrosols Treated with Direct Electric Current as Coatings for Sausages
Polymers 2017, 9(11), 602; doi:10.3390/polym9110602
Received: 6 September 2017 / Revised: 7 November 2017 / Accepted: 8 November 2017 / Published: 11 November 2017
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Abstract
We investigated the effect of sodium alginate hydrosols (1%) with 0.2% of NaCl treated with direct electric current (DC) used as a coating on microbial (Total Viable Counts, Psychrotrophic bacteria, yeast and molds, Lactic acid bacteria, Enterobacteriaceae), physiochemical (pH, lipid oxidation, antioxidant
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We investigated the effect of sodium alginate hydrosols (1%) with 0.2% of NaCl treated with direct electric current (DC) used as a coating on microbial (Total Viable Counts, Psychrotrophic bacteria, yeast and molds, Lactic acid bacteria, Enterobacteriaceae), physiochemical (pH, lipid oxidation, antioxidant activity, weight loss, color) and sensory properties of skinned pork sausages or with artificial casing stored at 4 °C for 28 days. Moreover, the cytotoxicity analysis of sodium alginate hydrogels was performed. The results have shown that application of experimental coatings on the sausage surface resulted in reducing all tested groups of microorganisms compared to control after a 4-week storage. The cytotoxicity analysis revealed that proliferation of RAW 264.7 and L929 is not inhibited by the samples treated with 200 mA. Ferric reducing antioxidant power (FRAP) and free radical scavenging activity (DPPH) analyses showed that there are no significant differences in antioxidant properties between control samples and those covered with sodium alginate. After 28 days of storage, the highest value of thiobarbituric acid-reactive substances (TBARS) was noticed for variants treated with 400 mA (1.07 mg malondialdehyde/kg), while it was only slightly lower for the control sample (0.95 mg MDA/kg). The obtained results suggest that sodium alginate treated with DC may be used as a coating for food preservation because of its antimicrobial activity and lack of undesirable impact on the quality factors of sausages. Full article
(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)
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Open AccessArticle Comparative Study of the Durability Behaviors of Epoxy- and Polyurethane-Based CFRP Plates Subjected to the Combined Effects of Sustained Bending and Water/Seawater Immersion
Polymers 2017, 9(11), 603; doi:10.3390/polym9110603
Received: 1 October 2017 / Revised: 9 November 2017 / Accepted: 10 November 2017 / Published: 12 November 2017
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Abstract
In many applications, carbon fiber reinforced polymer (CFRP) composite materials suffer from the combined effects of sustained bending and immersion. In the present study, pultruded epoxy- and polyurethane (PU)-based CFRP plates were studied for their long-term performances, subjected to the combined effects of
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In many applications, carbon fiber reinforced polymer (CFRP) composite materials suffer from the combined effects of sustained bending and immersion. In the present study, pultruded epoxy- and polyurethane (PU)-based CFRP plates were studied for their long-term performances, subjected to the combined effects of water/seawater immersion and sustained bending (0%, 30%, and 58% of the ultimate strain). The water uptake and the evolution of the mechanical properties were investigated. In addition, the service lives of the CFRPs were predicted using the Arrhenius method. Generally, the sustained bending led to a decrease in the water uptake, and reduced the mechanical properties. A diffusion model, dividing the cross-section of CFRPs into the “less resin area” and “rich resin area”, was proposed to elucidate the variation of water uptake and mechanical properties. Compared to epoxy-based CFRPs, although PU-based CFRPs possessed a significantly higher water uptake, they exhibited better long-term performances in terms of mechanical properties. Full article
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Open AccessArticle Durability and Mechanical Performance of PMMA/Stone Sludge Nanocomposites for Acrylic Solid Surface Applications
Polymers 2017, 9(11), 604; doi:10.3390/polym9110604
Received: 4 September 2017 / Revised: 1 November 2017 / Accepted: 7 November 2017 / Published: 12 November 2017
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Abstract
Acrylic solid surface sheets were prepared by mixing different kinds of stone sludge fillers (SSF) in Poly (methyl methacrylate) (PMMA) nanocomposites. PMMA nanocomposite syrups were made using free radical polymerization of methylmethacrylate (MMA), then two kinds of nanofillers were added, namely, hydrophilic nanosilica
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Acrylic solid surface sheets were prepared by mixing different kinds of stone sludge fillers (SSF) in Poly (methyl methacrylate) (PMMA) nanocomposites. PMMA nanocomposite syrups were made using free radical polymerization of methylmethacrylate (MMA), then two kinds of nanofillers were added, namely, hydrophilic nanosilica and clay Halloysite nanotubules (HNTs). Acrylic solid surface sheets were manufactured by mixing the syrups with SSFs. The morphology of the produced sheets was studied using optical, and Scanning Electron Microscopy (SEM) that revealed the uniform distribution of stone sludge in the polymeric matrix. The study of the physical properties showed promising mechanical performance and durability of PMMA/SSF nanocomposites for acrylic solid surface applications. Full article
(This article belongs to the Special Issue Polymer-Clay (Nano)Composites)
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Open AccessArticle The In Vitro Enzymatic Degradation of Cross-Linked Poly(trimethylene carbonate) Networks
Polymers 2017, 9(11), 605; doi:10.3390/polym9110605
Received: 5 October 2017 / Revised: 27 October 2017 / Accepted: 8 November 2017 / Published: 13 November 2017
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Abstract
The in vitro enzymatic degradation of cross-linked poly(trimethylene carbonate) networks (PTMC-Ns) was performed in lipase solutions at 37 °C, and the effect of the initial molecular weight and cross-linker amount as well as the cross-linker type on the degradation rate of PTMC-Ns was
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The in vitro enzymatic degradation of cross-linked poly(trimethylene carbonate) networks (PTMC-Ns) was performed in lipase solutions at 37 °C, and the effect of the initial molecular weight and cross-linker amount as well as the cross-linker type on the degradation rate of PTMC-Ns was investigated. Due to their denser structure and more hydrophobic surface as well as the higher glass transition temperature, a slower degradation rate was seen for PTMC-Ns with high initial molecular weight at a given cross-linker amount. Similar results could be observed as the cross-linker amount increased, and cross-linker type also influenced the degradation rate of PTMC-Ns. Furthermore, the enzymatic degradation of PTMC-Ns was accelerated by the surfactants role of lipase via surface erosion mechanism, the enzymatic degradation rate was higher than that of hydrolysis case. The results indicated that PTMC-Ns were promising candidates for clinical subcutaneous implants, especially due to their tunable degradation rate and enhanced form-stability as well as no acidic degradation products. Full article
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Open AccessArticle Preparation of a Fluorocarbon Polymerizable Surfactant and Its Application in Emulsion Polymerization of Fluorine-Containing Acrylate
Polymers 2017, 9(11), 606; doi:10.3390/polym9110606
Received: 20 October 2017 / Revised: 7 November 2017 / Accepted: 10 November 2017 / Published: 14 November 2017
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Abstract
A novel polymerizable fluorocarbon surfactant, perfluoro (4–methyl–3, 6–dioxaoct–7–ene) sodium sulfonate (PSVNa), was synthesized and characterized. The fluorocarbon surfactant PSVNa and its mixture PSVNa/SDS were used as emulsifiers during the emulsion polymerization of DFHMA/MMA. The investigation of polymerization kinetics, particle size, and stability of
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A novel polymerizable fluorocarbon surfactant, perfluoro (4–methyl–3, 6–dioxaoct–7–ene) sodium sulfonate (PSVNa), was synthesized and characterized. The fluorocarbon surfactant PSVNa and its mixture PSVNa/SDS were used as emulsifiers during the emulsion polymerization of DFHMA/MMA. The investigation of polymerization kinetics, particle size, and stability of the emulsions revealed that PSVNa has excellent emulsifying properties. The NMR spectrum of the copolymer and the detection of residual PSVNa show that more than 95% of the fluorocarbon surfactants have been linked to the polymer chains by radical polymerization, which will greatly reduce the environmental pollution caused by fluorinated surfactants. Full article
(This article belongs to the Special Issue Fluorinated Polymers)
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Open AccessArticle Solid-State Polymerization of Poly(ethylene furanoate) Biobased Polyester, I: Effect of Catalyst Type on Molecular Weight Increase
Polymers 2017, 9(11), 607; doi:10.3390/polym9110607
Received: 26 October 2017 / Revised: 6 November 2017 / Accepted: 8 November 2017 / Published: 13 November 2017
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Abstract
In this work, we report the synthesis of poly(ethylene furanoate) (PEF), catalyzed by three different catalysts, namely, titanium (IV) isopropoxide (TIS), tetrabutyltitanate (TBT), and dibutyltin (IV) oxide (DBTO), via the two-stage melt polycondensation method. Solid-state polymerization (SSP) was conducted at different reaction times
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In this work, we report the synthesis of poly(ethylene furanoate) (PEF), catalyzed by three different catalysts, namely, titanium (IV) isopropoxide (TIS), tetrabutyltitanate (TBT), and dibutyltin (IV) oxide (DBTO), via the two-stage melt polycondensation method. Solid-state polymerization (SSP) was conducted at different reaction times (1, 2, 3.5, and 5 h) and temperatures 190, 200, and 205 °C, under vacuum. The resultant polymers were analyzed according to their intrinsic viscosity (IV), end groups (–COOH), and thermal properties, via differential scanning calorimetry. DSC results showed that the post polymerization process was favorable to enhance the melting point of the prepared PEF samples. As was expected, the intrinsic viscosity and the average molecular weight of PEF increased with the SSP time and temperature, whereas the number of carboxyl end-groups was decreased. A simple kinetic model was also developed and used to predict the time evolution of polymers IV, as well as the carboxyl and hydroxyl content of PEF during the SSP. From both the experimental measurements and the theoretical simulation results it was proved that the presence of the TIS catalyst resulted in higher transesterification kinetic rate constants and higher reaction rates. The activation energies were not much affected by the presence of different catalysts. Finally, using DBTO as a catalyst, the polyesters produced have higher crystallinity, and as a consequence, higher number of inactive carboxyl and hydroxyl groups. Full article
(This article belongs to the Special Issue Biodegradable and Biobased Polyesters)
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Open AccessArticle Allylthioketone Mediated Free Radical Polymerization of Methacrylates
Polymers 2017, 9(11), 608; doi:10.3390/polym9110608
Received: 17 October 2017 / Revised: 9 November 2017 / Accepted: 10 November 2017 / Published: 13 November 2017
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Abstract
By combination of high trapping free radical efficiency of the thioketone and resonance of the allylic radical, a new type of mediating agent, 1,3,3-triphenylprop-2-ene-1-thione (TPPT) has been successfully synthesized, and then is used to study controlled free radical polymerization of methacrylates. Very stable
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By combination of high trapping free radical efficiency of the thioketone and resonance of the allylic radical, a new type of mediating agent, 1,3,3-triphenylprop-2-ene-1-thione (TPPT) has been successfully synthesized, and then is used to study controlled free radical polymerization of methacrylates. Very stable TPPT radicals at the end of poly(methyl methacrylate) (PMMA) are detected in the polymerization of MMA using TPPT and AIBN as the control agent and initiator. The MALDI-TOF MS spectra are used to identify terminal groups of the resultant poly(glycidyl methacrylate) (PGMA), and major component of the obtained polymer has the structure, (CH3)2(CN)C-PGMA-C7H9O3. Chain extension reaction tests ascertain formation of the dead polymers during the polymer storage and purification process of the polymers. Owing to very slow fragmentation reaction of the TPPT-terminated polymethacrylate radical and addition reaction of this radical with a primary radical, the growing chain radicals are difficult to be regenerated, leading to an unobvious change of the molecular weight with monomer conversion. The molecular weights of polymers can be controlled by the ratios of monomer/initiator and TPPT/initiator. However, the first order kinetics of the polymerization and the polymers with narrow polydispersity are obtained, and these phenomena are discussed. This study provides useful information on how to design a better controlling agent. Full article
(This article belongs to the Special Issue Living Polymerization)
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Open AccessArticle Effect of CO2 Laser Treatment on the Fabric Hand of Cotton and Cotton/Polyester Blended Fabric
Polymers 2017, 9(11), 609; doi:10.3390/polym9110609
Received: 20 October 2017 / Revised: 31 October 2017 / Accepted: 8 November 2017 / Published: 13 November 2017
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Abstract
This paper compares the impact of laser treatment on cotton and cotton/polyester blended fabric hand properties, using the PhabrOmeter system. Five fabric hand properties, namely, stiffness, smoothness, softness, wrinkle recovery rate, and drapability, were obtained, and it was proven that laser treatment could
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This paper compares the impact of laser treatment on cotton and cotton/polyester blended fabric hand properties, using the PhabrOmeter system. Five fabric hand properties, namely, stiffness, smoothness, softness, wrinkle recovery rate, and drapability, were obtained, and it was proven that laser treatment could be successfully used to change the fabric hand. In the case of pure cotton woven fabrics, the fabrics were found to have better drapability and wrinkle recovery after laser treatment. In cotton/polyester blended fabrics, stiffness was found to be relatively higher after laser irradiation. Full article
(This article belongs to the Special Issue Textile and Textile-Based Materials)
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Open AccessArticle Synthesis of Terpolymers with Homogeneous Composition by Free Radical Copolymerization of Maleic Anhydride, Perfluorooctyl and Butyl or Dodecyl Methacrylates: Application of the Continuous Flow Monomer Addition Technique
Polymers 2017, 9(11), 610; doi:10.3390/polym9110610
Received: 9 October 2017 / Revised: 3 November 2017 / Accepted: 9 November 2017 / Published: 13 November 2017
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Abstract
Terpolymers of homogeneous composition were prepared by free radical copolymerization of butyl or dodecyl methacrylate, 1H,1H,2H,2H-perfluorodecyl methacrylate and maleic anhydride using the continuous monomer addition technique. The copolymerization reactions were performed at 65 °C in
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Terpolymers of homogeneous composition were prepared by free radical copolymerization of butyl or dodecyl methacrylate, 1H,1H,2H,2H-perfluorodecyl methacrylate and maleic anhydride using the continuous monomer addition technique. The copolymerization reactions were performed at 65 °C in the presence of azobisisobutyronitrile as an initiator in a mixture of methyl ethyl ketone and 1,3-bis (trifluoromethyl)benzene. The monomers and initiator are added to the reaction mixture with the same rate they are consumed in 5- and 10-fold excess compared to the initial monomer stock. The obtained terpolymers with molecular weights Mn = 50,000–70,000 are of uniform composition, close to the composition determined in low conversion experiments, proving the principle of the chosen concept. The kinetic data necessary for the design of the continuous addition experiment were obtained from binary copolymerization experiments at low monomer conversion (to avoid compositional drift). In addition, the so-called terpolymerization parameter was determined from ternary copolymerization experiments. Full article
(This article belongs to the Special Issue Fluorinated Polymers)
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Open AccessArticle Aggregation Behavior of Nano-Silica in Polyvinyl Alcohol/Polyacrylamide Hydrogels Based on Dissipative Particle Dynamics
Polymers 2017, 9(11), 611; doi:10.3390/polym9110611
Received: 28 October 2017 / Accepted: 10 November 2017 / Published: 14 November 2017
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Abstract
Due to the aggregation behavior of nano-silica in aqueous solution, the use of nano-silica without surface modification for synthesizing hydrogels is still a challenging task. This paper presents our study on the use of dissipative particle dynamics simulations to discover the aggregation behavior
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Due to the aggregation behavior of nano-silica in aqueous solution, the use of nano-silica without surface modification for synthesizing hydrogels is still a challenging task. This paper presents our study on the use of dissipative particle dynamics simulations to discover the aggregation behavior of nano-silica in polyvinyl alcohol (PVA)/polyacrylamide (PAM) blended hydrogels. By simulations, we aimed at investigating the effects of such factors as nano-silica content, polymer component ratio, temperature and shear rate on the aggregation behavior of nano-silica in terms of the mesoscopic morphologies and the relative concentration distribution functions. Our results reveal that the dispersion of nano-silica is seen if the nano-silica content is increased to 1.5%, and the aggregation of nano-silica becomes noticeable in blended hydrogels with an increase in the nano-silica content. This finding agrees well with the experimental results obtained by means of scanning electron microscopy. Furthermore, it is also found that the dispersion of nano-silica becomes more uniform with an increase in PAM content, temperature and shear rate. These findings greatly enrich our understanding of the aggregation behavior of nano-silica in PVA/PAM blended hydrogels. Full article
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Open AccessFeature PaperArticle Binding of the GTPase Sar1 to a Lipid Membrane Monolayer: Insertion and Orientation Studied by Infrared Reflection–Absorption Spectroscopy
Polymers 2017, 9(11), 612; doi:10.3390/polym9110612
Received: 2 October 2017 / Revised: 26 October 2017 / Accepted: 6 November 2017 / Published: 14 November 2017
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Abstract
Membrane-interacting proteins are polyphilic polymers that engage in dynamic protein–protein and protein–lipid interactions while undergoing changes in conformation, orientation and binding interfaces. Predicting the sites of interactions between such polypeptides and phospholipid membranes is still a challenge. One example is the small eukaryotic
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Membrane-interacting proteins are polyphilic polymers that engage in dynamic protein–protein and protein–lipid interactions while undergoing changes in conformation, orientation and binding interfaces. Predicting the sites of interactions between such polypeptides and phospholipid membranes is still a challenge. One example is the small eukaryotic GTPase Sar1, which functions in phospholipid bilayer remodeling and vesicle formation as part of the multimeric coat protein complex (COPII). The membrane interaction of Sar1 is strongly dependent on its N-terminal 23 amino acids. By monolayer adsorption experiments and infrared reflection-absorption spectroscopy (IRRAS), we elucidate the role of lipids in inducing the amphipathicity of this N-terminal stretch, which inserts into the monolayer as an amphipathic helix (AH). The AH inserting angle is determined and is consistent with the philicities and spatial distribution of the amino acid monomers. Using an advanced method of IRRAS data evaluation, the orientation of Sar1 with respect to the lipid layer prior to the recruitment of further COPII proteins is determined. The result indicates that only a slight reorientation of the membrane-bound Sar1 is needed to allow coat assembly. The time-course of the IRRAS analysis corroborates a role of slow GTP hydrolysis in Sar1 desorption from the membrane. Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessArticle Effect of the GO Reduction Method on the Dielectric Properties, Electrical Conductivity and Crystalline Behavior of PEO/rGO Nanocomposites
Polymers 2017, 9(11), 613; doi:10.3390/polym9110613
Received: 29 September 2017 / Revised: 29 October 2017 / Accepted: 11 November 2017 / Published: 14 November 2017
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Abstract
The effect of the reduction method to prepare reduced graphene oxide (rGO) on the melt linear viscoelastic properties, electrical conductivity, polymer matrix crystalline behavior and dielectric properties of PEO-rGO nanocomposites was investigated. Reduction was performed chemically with either sodium borohydride (NaBH4)
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The effect of the reduction method to prepare reduced graphene oxide (rGO) on the melt linear viscoelastic properties, electrical conductivity, polymer matrix crystalline behavior and dielectric properties of PEO-rGO nanocomposites was investigated. Reduction was performed chemically with either sodium borohydride (NaBH4) or hydrazine monohydrate (N2H4·H2O) or both reduction agents consecutively as well as thermally at 1000 °C. The different reduction methods resulted in exfoliated rGO sheets with different types and amounts of remaining functional groups, as indicated by FT-IR, Raman, TGA and XRD characterization. Moreover, their electrical conductivity ranged between 10−4 and 10−1 S/cm, with the consecutive use of both chemical reduction agents being far superior. PEO nanocomposites with filler loadings of 0.5 wt %, 1 wt % and 2 wt % were prepared by solvent mixing. The rGO fillers affected the melt linear viscoelastic and crystalline behavior of the PEO matrix and resulted in nanocomposites with a substantially increased electrical conductivity. Despite the wide variability in filler conductivity, the effects on the polymer nanocomposite properties were less distinctive. A correlation was obtained between the reduction of the mobility of the polymer chains (evaluated by the glass transition temperature) and the dielectric strength of the interfacial polarisation originating from the effective entrapment of GO/rGO filler charges at the interface with the less conductive PEO. Thus, favorable interactions of the polar PEO with the filler led to reduced mobility of the PEO chains and thereby a more effective entrapment of the filler charges at the PEO interface. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle Short Oxygen Plasma Treatment Leading to Long-Term Hydrophilicity of Conductive PCL-PPy Nanofiber Scaffolds
Polymers 2017, 9(11), 614; doi:10.3390/polym9110614
Received: 15 September 2017 / Revised: 1 November 2017 / Accepted: 8 November 2017 / Published: 14 November 2017
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Abstract
Electrically conductive scaffolds are of significant interest in tissue regeneration. However, the chemistry of the existing scaffolds usually lacks the bioactive features for effective interaction with cells. In this study, poly(ε-caprolactone) was electrospun into aligned nanofibers with 0.58 µm average diameter. Electrospinning was
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Electrically conductive scaffolds are of significant interest in tissue regeneration. However, the chemistry of the existing scaffolds usually lacks the bioactive features for effective interaction with cells. In this study, poly(ε-caprolactone) was electrospun into aligned nanofibers with 0.58 µm average diameter. Electrospinning was followed by polypyrrole coating on the surface of the fibers, which resulted in 48 kΩ/sq surface resistivity. An oxygen plasma treatment was conducted to change the hydrophobic surface of the fiber mats into a hydrophilic substrate. The water contact angle was reduced from 136° to 0°, and this change remained on the surface of the material even after one year. An indirect cytotoxicity test was conducted, which showed cytocompatibility of the fibrous scaffolds. To measure the cell growth on samples, fibroblast cells were cultured on fibers for 7 days. The cell distribution and density were observed and calculated based on confocal images taken of the cell culture experiment. The number of cells on the plasma-treated sample was more than double than that of sample without plasma treatment. The long-lasting hydrophilicity of the plasma treated fibers with conductive coating is the significant contribution of this work for regeneration of electrically excitable tissues. Full article
(This article belongs to the Special Issue Biodegradable and Biobased Polyesters)
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Open AccessArticle Effect of Ammonium Polyphosphate to Aluminum Hydroxide Mass Ratio on the Properties of Wood-Flour/Polypropylene Composites
Polymers 2017, 9(11), 615; doi:10.3390/polym9110615
Received: 11 October 2017 / Revised: 8 November 2017 / Accepted: 12 November 2017 / Published: 14 November 2017
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Abstract
Two halogen-free inorganic flame retardants, ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were added to wood-flour/polypropylene composites (WPCs) at different APP to ATH mass ratios (APP/ATH ratios), with a constant total loading of 30 wt % (30% by mass). Water soaking tests indicated
[...] Read more.
Two halogen-free inorganic flame retardants, ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were added to wood-flour/polypropylene composites (WPCs) at different APP to ATH mass ratios (APP/ATH ratios), with a constant total loading of 30 wt % (30% by mass). Water soaking tests indicated a low hygroscopicity and/or solubility of ATH as compared to APP. Mechanical property tests showed that the flexural properties were not significantly affected by the APP/ATH ratio, while the impact strength appeared to increase with the increasing ATH/APP ratio. Cone calorimetry indicated that APP appeared to be more effective than ATH in reducing the peak of heat release rate (PHRR). However, when compared to the neat WPCs, total smoke release decreased with the addition of ATH but increased with the addition of APP. Noticeably, WPCs containing the combination of 20 wt % APP and 10 wt % ATH (WPC/APP-20/ATH-10) showed the lowest PHRR and total heat release in all of the formulations. WPCs combustion residues were analyzed by scanning electron microscopy, laser Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis coupled with FTIR spectroscopy was used to identify the organic volatiles that were produced during the thermal decomposition of WPCs. WPC/APP-20/ATH-10 showed the most compact carbonaceous residue with the highest degree of graphitization. Full article
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Open AccessArticle Ionic Conductivity and Assembled Structures of Imidazolium Salt-Based Block Copolymers with Thermoresponsive Segments
Polymers 2017, 9(11), 616; doi:10.3390/polym9110616
Received: 4 October 2017 / Revised: 9 November 2017 / Accepted: 10 November 2017 / Published: 15 November 2017
PDF Full-text (2193 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ionic liquid-based block copolymers composed of ionic (solubility tunable)–nonionic (water-soluble and thermoresponsive) segments were synthesized to explore the relationship between ionic conductivity and assembled structures. Three block copolymers, comprising poly(N-vinylimidazolium bromide) (poly(NVI-Br)) as a hydrophilic poly(ionic liquid) segment and thermoresponsive poly(
[...] Read more.
Ionic liquid-based block copolymers composed of ionic (solubility tunable)–nonionic (water-soluble and thermoresponsive) segments were synthesized to explore the relationship between ionic conductivity and assembled structures. Three block copolymers, comprising poly(N-vinylimidazolium bromide) (poly(NVI-Br)) as a hydrophilic poly(ionic liquid) segment and thermoresponsive poly(N-isopropylacrylamide) (poly(NIPAM)), having different compositions, were initially prepared by RAFT polymerization. The anion-exchange reaction of the poly(NVI-Br) in the block copolymers with lithium bis(trifluoromethanesulfonyl)imide (LiNTf2) proceeded selectively to afford amphiphilic block copolymers composed of hydrophobic poly(NVI-NTf2) and hydrophilic poly(NIPAM). Resulting poly(NVI-NTf2)-b-poly(NIPAM) exhibited ionic conductivities greater than 10−3 S/cm at 90 °C and 10−4 S/cm at 25 °C, which can be tuned by the comonomer composition and addition of a molten salt. Temperature-dependent ionic conductivity and assembled structures of these block copolymers were investigated, in terms of the comonomer composition, nature of counter anion and sample preparation procedure. Full article
(This article belongs to the Special Issue Polymers and Block Copolymers at Interfaces and Surfaces)
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Open AccessArticle Thiolated Chitosan Masked Polymeric Microspheres with Incorporated Mesocellular Silica Foam (MCF) for Intranasal Delivery of Paliperidone
Polymers 2017, 9(11), 617; doi:10.3390/polym9110617
Received: 30 October 2017 / Revised: 8 November 2017 / Accepted: 13 November 2017 / Published: 15 November 2017
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Abstract
In this study, mesocellular silica foam (MCF) was used to encapsulate paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. MCF with the drug adsorbed was further encapsulated into poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) 75/25 w/w
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In this study, mesocellular silica foam (MCF) was used to encapsulate paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. MCF with the drug adsorbed was further encapsulated into poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) 75/25 w/w microspheres and these have been coated with thiolated chitosan. As found by TEM analysis, thiolated chitosan formed a thin layer on the polymeric microspheres’ surface and was used in order to enhance their mucoadhesiveness. These microspheres aimed at the intranasal delivery of paliperidone. The DSC and XRD studies showed that paliperidone was encapsulated in amorphous form inside the MCF silica and for this reason its dissolution profile was enhanced compared to the neat drug. In coated microspheres, thiolated chitosan reduced the initial burst effect of the paliperidone dissolution profile and in all cases sustained release formulations have been prepared. The release mechanism was also theoretically studied and three kinetic models were proposed and successfully fitted for a dissolution profile of prepared formulations to be found. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle The Effect of Fluid Shear Stress on the In Vitro Release Kinetics of Sirolimus from PLGA Films
Polymers 2017, 9(11), 618; doi:10.3390/polym9110618
Received: 17 August 2017 / Revised: 31 October 2017 / Accepted: 10 November 2017 / Published: 15 November 2017
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Abstract
Drug-carrying coatings of stents implanted in blood vessels are exposed to various blood flows. This study investigated the effect of fluid shear stress on the in vitro release kinetics of sirolimus from poly(lactic-co-glycolic acid) (PLGA) films. The homemade parallel plate flow
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Drug-carrying coatings of stents implanted in blood vessels are exposed to various blood flows. This study investigated the effect of fluid shear stress on the in vitro release kinetics of sirolimus from poly(lactic-co-glycolic acid) (PLGA) films. The homemade parallel plate flow chamber was used to exert quantitative shear stress on the sirolimus-carrying film. By adjusting the flow rate of the release media in the chamber, three levels of shear stress (3.6, 12.0, and 36.0 dyn/cm2) were respectively applied. For each level of shear stress employed, the release kinetics of sirolimus from the PLGA films exhibited a four-phase profile: an initial burst release phase (Phase I), a lag phase (Phase II), a second burst release phase (Phase III), and a terminal release phase (Phase IV). During Phases I and II, sirolimus was released slowly and in small amounts (<10%); however, during Phases III and IV, the drug release increased considerably. Comparisons of different shear stresses indicated that greater shear stress resulted in earlier and faster sirolimus release, with more cumulative drug release observed. PLGA film degradations (molecular weight reduction, mass loss, and surface topographical variations) were also investigated to better explain the observed drug release behavior. Consequently, fluid shear stress was found to significantly accelerate the release of sirolimus from the PLGA matrices. Therefore, this study could provide a practical method for evaluating the in vitro drug release from polymer matrices under uniform shear stress, and might help improve the design of biodegradable coatings on drug-eluting stents. Full article
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Open AccessArticle Effect of the Addition of Carbon Nanomaterials on Electrical and Mechanical Properties of Wood Plastic Composites
Polymers 2017, 9(11), 620; doi:10.3390/polym9110620
Received: 13 October 2017 / Revised: 10 November 2017 / Accepted: 11 November 2017 / Published: 16 November 2017
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Abstract
Wood Plastic Composites (WPCs) are a new generation of green composites that could optimize the use of harvested trees and increase the entire value chain. In this study, the electrical and mechanical properties of WPCs containing carbon blacks (CB), flake graphite (FG) and
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Wood Plastic Composites (WPCs) are a new generation of green composites that could optimize the use of harvested trees and increase the entire value chain. In this study, the electrical and mechanical properties of WPCs containing carbon blacks (CB), flake graphite (FG) and carbon nanotubes (CNTs) have been investigated. The electrical property of WPCs is improved significantly owing to the introduction of these carbon nanomaterial fillers. The volume and surface resistivity values of the investigated composites all obviously decreased with the increase in filler content, especially CNTs, which displayed the most satisfactory results. Based on a series of laboratory experiments carried out to investigate the mechanical performance, it can be concluded that the addition of the carbon nanomaterial fillers decreases the mechanical properties of WPCs slightly with the increase in filler content because of the weak interfacial interactions between the fillers and polymer matrix. Full article
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Open AccessArticle Cardanol Groups Grafted on Poly(vinyl chloride)—Synthesis, Performance and Plasticization Mechanism
Polymers 2017, 9(11), 621; doi:10.3390/polym9110621
Received: 8 September 2017 / Revised: 9 November 2017 / Accepted: 11 November 2017 / Published: 15 November 2017
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Abstract
Internally plasticized poly(vinyl chloride) (PVC) materials are investigated via grafting of propargyl ether cardanol (PEC). The chemical structure of the materials was studied by FT-IR and 1H NMR. The performace of the obtained internally plasticized PVC materials was also investigated with TGA,
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Internally plasticized poly(vinyl chloride) (PVC) materials are investigated via grafting of propargyl ether cardanol (PEC). The chemical structure of the materials was studied by FT-IR and 1H NMR. The performace of the obtained internally plasticized PVC materials was also investigated with TGA, DSC and leaching tests. The results showed that grafting of propargyl ether cardanol (PEC) on PVC increased the free volume and distance of PVC chains, which efficiently decreased the glass transition temperature (Tg). No migration was found in the leaching tests for internally plasticized PVC films compared with plasticized PVC materials with commercial plasticizer dioctyl phthalate (DOP). The internal plasticization mechanism was also disscussed according to lubrication theory and free volume theory. This work provides a meaningful strategy for designing no-migration PVC materials by introducing cardanol groups as branched chains. Full article
(This article belongs to the Special Issue Polymers from Renewable Resources)
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Open AccessArticle Effect of PVA Blending on Structural and Ion Transport Properties of CS:AgNt-Based Polymer Electrolyte Membrane
Polymers 2017, 9(11), 622; doi:10.3390/polym9110622
Received: 16 October 2017 / Revised: 9 November 2017 / Accepted: 13 November 2017 / Published: 15 November 2017
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Abstract
In this work, the role of poly(vinyl alcohol) (PVA) blending on structural and electrical properties of chitosan:silver nitrate systems is studied. The X-ray diffraction (XRD) results show that the crystalline phase of chitosan (CS) is greatly scarified by silver nitrate (AgNt) salt. The
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In this work, the role of poly(vinyl alcohol) (PVA) blending on structural and electrical properties of chitosan:silver nitrate systems is studied. The X-ray diffraction (XRD) results show that the crystalline phase of chitosan (CS) is greatly scarified by silver nitrate (AgNt) salt. The crystalline domain of CS:AgNt is more broadened at 10 wt % of PVA. The spike and semicircular arcs can be separated in impedance plots. At high temperatures, the spike regions remained. The direct current (DC) conductivity was calculated from the bulk resistance obtained from the impedance plots. The dielectric constant and DC conductivity versus PVA content exhibited similar behavior. The maximum DC conductivity at ambient temperature was 1.1 × 10−6 S/cm for 10 wt % of PVA. The DC ionic conductivity increased to 9.95 × 10−5 S/cm at 80 °C. Above 10 wt % of PVA, the drop in DC conductivity and dielectric constant were observed due to the increase in viscosity. Shifting of relaxation peaks towards the lower frequency revealed the increase of resistivity of the samples. The linear increase of DC conductivity versus 1000/T indicated that ion transport followed the Arrhenius model. The incomplete semicircular arc in Argand plots indicated the non-Debye type of relaxation process. The Argand plots were used to distinguish between conductivity relaxation and viscoelastic relaxation. Three regions were distinguished in the alternating current (AC) spectra of the blend electrolyte samples. The plateau region in AC spectra was used to estimate the DC conductivity. The estimated DC conductivity from the AC spectra was close to those calculated from the impedance plots. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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Open AccessArticle Styrene-Assisted Maleic Anhydride Grafted Poly(lactic acid) as an Effective Compatibilizer for Wood Flour/Poly(lactic acid) Bio-Composites
Polymers 2017, 9(11), 623; doi:10.3390/polym9110623
Received: 13 October 2017 / Revised: 4 November 2017 / Accepted: 12 November 2017 / Published: 15 November 2017
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Abstract
This study aimed to evaluate the effect of styrene-assisted maleic anhydride-grafted poly(lactic acid) (PLA-g-St/MAH) on the interfacial properties of wood flour/poly(lactic acid) (PLA) bio-composites. PLA-g-St/MAH was synthesized by free-radical melt grafting using styrene as a comonomer and dicumyl peroxide
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This study aimed to evaluate the effect of styrene-assisted maleic anhydride-grafted poly(lactic acid) (PLA-g-St/MAH) on the interfacial properties of wood flour/poly(lactic acid) (PLA) bio-composites. PLA-g-St/MAH was synthesized by free-radical melt grafting using styrene as a comonomer and dicumyl peroxide as an initiator. The structure of PLA-g-St/MAH was characterized by Fourier transform infrared spectroscopy. Wood flour/PLA composites were prepared by compression molding using PLA-g-St/MAH as a compatibilizer. The effects of PLA-g-St/MAH on the rheological and mechanical properties, as well as on the fractured surface morphology of the composites were investigated. Results indicated that storage modulus, complex viscosity, equilibrium torque, and shear heat were significantly increased. The mechanical properties of the wood flour/PLA composites were also significantly increased after the addition of PLA-g-St/MAH. The maximum values were achieved at the loading rate of 3 wt % because of the improved interfacial adhesion between the wood flour and the PLA matrix. Full article
(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)
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Open AccessArticle Polymeric Amines and Ampholytes Derived from Poly(acryloyl chloride): Synthesis, Influence on Silicic Acid Condensation and Interaction with Nucleic Acid
Polymers 2017, 9(11), 624; doi:10.3390/polym9110624
Received: 28 October 2017 / Revised: 12 November 2017 / Accepted: 13 November 2017 / Published: 16 November 2017
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Abstract
Polymeric amines are intensively studied due to various valuable properties. This study describes the synthesis of new polymeric amines and ampholytes by the reaction of poly(acryloyl chloride) with trimethylene-based polyamines containing one secondary and several (1–3) tertiary amine groups. The polymers contain polyamine
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Polymeric amines are intensively studied due to various valuable properties. This study describes the synthesis of new polymeric amines and ampholytes by the reaction of poly(acryloyl chloride) with trimethylene-based polyamines containing one secondary and several (1–3) tertiary amine groups. The polymers contain polyamine side chains and carboxylic groups when the polyamine was in deficiency. These polymers differ in structure of side groups, but they are identical in polymerization degree and polydispersity, which facilitates the study of composition-properties relationships. The structure of the obtained polymers was confirmed with 13C nuclear magnetic resonance infrared spectroscopy, and acid-base properties were studied with potentiometry titration. Placement of the amine groups in the side chains influences their acid-base properties: protonation of the amine group exerts a larger impact on the amine in the same side chain than on the amines in the neighboring side chains. The obtained polymers are prone to aggregation in aqueous solutions tending to insolubility at definite pH values in the case of polyampholytes. Silicic acid condensation in the presence of new polymers results in soluble composite nanoparticles and composite materials which consist of ordered submicrometer particles according to dynamic light scattering and electron microscopy. Polymeric amines, ampholytes, and composite nanoparticles are capable of interacting with oligonucleotides, giving rise to complexes that hold promise for gene delivery applications. Full article
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Open AccessArticle Equilibrium Melting Temperature of Polymorphic Poly(l-lactide) and Its Supercooling Dependence on Growth Kinetics
Polymers 2017, 9(11), 625; doi:10.3390/polym9110625
Received: 19 October 2017 / Revised: 8 November 2017 / Accepted: 14 November 2017 / Published: 16 November 2017
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Abstract
In this study, the isothermal crystallization process of poly(l-lactide) (PLLA) has been investigated using in situ XRD, differential scanning calorimetry (DSC), and polarized optical microscopy (POM). Linear and nonlinear extrapolation methods have been deployed to estimate the equilibrium melting temperature (
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In this study, the isothermal crystallization process of poly(l-lactide) (PLLA) has been investigated using in situ XRD, differential scanning calorimetry (DSC), and polarized optical microscopy (POM). Linear and nonlinear extrapolation methods have been deployed to estimate the equilibrium melting temperature ( T m 0 ), which is used for analyzing the supercooling dependence of the PLLA spherulitic growth rate (G). A double-melting behavior observed for PLLA under crystallization Tc < 120 °C has been attributed to the formation of both α′ and α crystals. The T m 0 values of both α′ and α crystals have been evaluated using the linear method (172.8 °C) and nonlinear method (196.4 °C), with the nonlinear estimate being 23.6 °C higher. A discontinuity in the temperature dependence of spherulite growth rate is observed around 128.3 °C. Regime II–III transition is found to occur at 128.3 °C when T m 0 = 196.4 °C as estimated by the nonlinear extrapolation method. Full article
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Open AccessArticle From Insulating PMMA Polymer to Conjugated Double Bond Behavior: Green Chemistry as a Novel Approach to Fabricate Small Band Gap Polymers
Polymers 2017, 9(11), 626; doi:10.3390/polym9110626
Received: 11 October 2017 / Revised: 5 November 2017 / Accepted: 14 November 2017 / Published: 16 November 2017
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Abstract
Dye-doped polymer films of Poly(methyl methacrylate) PMMA have been prepared with the use of the conventional solution cast technique. Natural dye has been extracted from environmentally friendly material of green tea (GT) leaves. Obvious Fourier transform infrared (FTIR) spectra for the GT extract
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Dye-doped polymer films of Poly(methyl methacrylate) PMMA have been prepared with the use of the conventional solution cast technique. Natural dye has been extracted from environmentally friendly material of green tea (GT) leaves. Obvious Fourier transform infrared (FTIR) spectra for the GT extract were observed, showing absorption bands at 3401 cm−1, 1628 cm−1, and 1029 cm−1, corresponding to O–H/N–H, C=O, and C–O groups, respectively. The shift and decrease in the intensity of the FTIR bands in the doped PMMA sample have been investigated to confirm the complex formation between the GT dye and PMMA polymer. Different types of electronic transition could be seen in the absorption spectra of the dye-doped samples. For the PMMA sample incorporated with 28 mL of GT dye, distinguishable intense peak around 670 nm appeared, which opens new frontiers in the green chemistry field that are particularly suitable for laser technology and optoelectronic applications. The main result of this study showed that the doping of the PMMA polymer with green tea dye exhibited a strong absorption peak around 670 nm in the visible range. The absorption edge was found to be shifted towards the lower photon energy for the doped samples. Optical dielectric loss and Tauc’s model were used to estimate the optical band gaps of the samples and to specify the transition types between the valence band (VB) and conduction band (CB), respectively. A small band gap of around 2.6 eV for the dye-doped PMMA films was observed. From the scientific and engineering viewpoints, this topic has been found to be very important and relevant. The amorphous nature of the doped samples was found and ascribed to the increase of Urbach energy. The Urbach energy has been correlated to the analysis of X-ray diffraction (XRD) to display the structure-properties relationships. Full article
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Open AccessArticle MgCl2-Supported Titanium Ziegler-Natta Catalyst Using Carbon Dioxide-Based Poly(propylene ether carbonate) Diols as Internal Electron Donor for 1-Butene Polymerization
Polymers 2017, 9(11), 627; doi:10.3390/polym9110627
Received: 10 October 2017 / Revised: 4 November 2017 / Accepted: 14 November 2017 / Published: 17 November 2017
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Abstract
MgCl2-supported titanium Ziegler-Natta catalyst containing CO2-based poly(propylene ether carbonate) diols as a potential internal electron donor (IED) was synthesized and employed for 1-butene polymerization. When compared with the Ziegler-Natta catalyst using poly(polypropylene glycol) as IED, the catalyst prepared with
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MgCl2-supported titanium Ziegler-Natta catalyst containing CO2-based poly(propylene ether carbonate) diols as a potential internal electron donor (IED) was synthesized and employed for 1-butene polymerization. When compared with the Ziegler-Natta catalyst using poly(polypropylene glycol) as IED, the catalyst prepared with poly(propylene ether carbonate) diols showed good particle morphology, higher activity and stereoselectivity. The results suggested that existence of the carbonate group within the structure of poly(propylene ether carbonate) diols truly plays an important role in improving the performance of the catalyst for the 1-butene polymerization. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessArticle The Dynamic Mechanical Analysis of Highly Filled Rice Husk Biochar/High-Density Polyethylene Composites
Polymers 2017, 9(11), 628; doi:10.3390/polym9110628
Received: 27 October 2017 / Revised: 14 November 2017 / Accepted: 15 November 2017 / Published: 17 November 2017
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Abstract
In this study, rice husk biochar/high-density polyethylene (HDPE) composites were prepared via melt mixing followed by extrusion. Effects of biochar content and testing temperature on the dynamic mechanical analysis (DMA) of the composites were studied. Morphological analysis of the rice husk biochar and
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In this study, rice husk biochar/high-density polyethylene (HDPE) composites were prepared via melt mixing followed by extrusion. Effects of biochar content and testing temperature on the dynamic mechanical analysis (DMA) of the composites were studied. Morphological analysis of the rice husk biochar and composites were evaluated by scanning electron microscopy (SEM). The results showed that biochar had a positive effect on dynamic viscoelasticity, creep resistance and stress relaxation properties of the composites, but the creep resistance and stress relaxation of the composites decreased with the increase of temperature. SEM analysis showed that HDPE components were embedded in the holes of the rice husk biochar, and it is believed that strong interaction was achieved. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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