Showing papers in "Journal of Applied Polymer Science in 2015"

Recent advances in nanocellulose for biomedical applications

Abstract: Nanocellulose materials have undergone rapid development in recent years as promising biomedical materials because of their excellent physical and biological properties, in particular their biocompatibility, biodegradability, and low cytotoxicity. Recently, a significant amount of research has been directed toward the fabrication of advanced cellulose nanofibers with different morphologies and functional properties. These nanocellulose fibers are widely applied in medical implants, tissue engineering, drug delivery, wound-healing, cardiovascular applications, and other medical applications. In this review, we reflect on recent advancements in the design and fabrication of advanced nanocellulose-based biomaterials (cellulose nanocrystals, bacterial nanocellulose, and cellulose nanofibrils) that are promising for biomedical applications and discuss material requirements for each application, along with the challenges that the materials might face. Finally, we give an overview on future directions of nanocellulose-based materials in the biomedical field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41719.

Understanding and guiding the phase inversion process for synthesis of solvent resistant nanofiltration membranes

Abstract: Since its introduction in membrane technology in the 1960's, phase inversion by means of immersion precipitation has been widely studied for the preparation of membranes to be applied in the fields of microfiltration (MF) and ultrafiltration (UF). However, much less knowledge is available about this process in terms of integrally skinned asymmetric nanofiltration membranes, especially for more hydrophobic polymers applied in solvent resistant nanofiltration (SRNF). This review focuses on the preparation aspects of integrally skinned asymmetric membranes to be applied in the field of SRNF via phase inversion. It starts with the explanation of the basic principles of the phase inversion process, covering both thermodynamic and kinetic aspects. Further, it summarizes the parameters that significantly influence final membrane performance and morphology, including polymer type and concentration, casting solvent, additives, evaporation time, and temperature, humidity, membrane thickness, composition, and temperature of coagulation bath and post-treatment. Literature contained within this review constitutes the core references in the field of SRNF, but also several references on preparation of MF, UF, aqueous NF, and reverse osmosis (RO) membranes have been included to better clarify or illustrate certain aspects of the process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42130.

Xanthan gum: a versatile biopolymer for biomedical and technological applications

Abstract: Xanthan gum is an extracellular polymer produced mainly by the bacterium Xanthomonas campestris. Traditionally it plays an important role in industrial applications as thickener, emulsion stabilizer and it has been added to water-based drilling fluids due to its pseudoplastic behavior and thermal stability. The structural properties of xanthan in solution can be tuned by the temperature and ionic strength; under high ionic strength or low temperature, xanthan chains are arranged in helical conformation, whereas under low ionic strength or high temperature, xanthan chains are coiled. Xanthan high molecular weight favors the building up of physical and chemical networks, which have been used as carriers for drugs and proteins and as scaffolds for cells. In combination with other polymers xanthan has been applied as excipient in tablets or as supporting hydrogels for drug release applications, particularly due to its acid resistance. The large versatility of xanthan gum opens the possibility for the creation of new architectures and additional applications involving this fascinating polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42035.

The organic electrochemical transistor for biological applications

Abstract: The rising field of bioelectronics, which couples the realms of electronics and biology, holds huge potential for the development of novel biomedical devices for therapeutics and diagnostics. Organic electronic devices are particularly promising; the use of robust organic electronic materials provides an ideal biointerface due to their reported biocompatibility, and mechanical matching between the sensor element and the biological environment, are amongst the advantages unique to this class of materials. One promising device emerging from this field is the organic electrochemical transistor (OECT). Arguably, the most important feature of an OECT is that it provides local amplification and as such can be used as a high fidelity transducer of biological events. Additionally, the OECT combines properties and characteristics that can be tuned for a wide spectrum of biological applications. Here, we frame the development of the OECT with respect to its underlying optimization for a variety of different applications, including ion sensing, enzymatic sensing, and electrophysiology. These applications have allowed the development of OECTs to sense local ionic/biomolecular and single cell activity, as well characterization of tissue and even monitoring of function of whole organs. The body of work reviewed here demonstrates that the OECT is an extremely versatile device that emerges as an important player for therapeutics and diagnostics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41735.

A review of the developments of characteristics of PEI derivatives for gene delivery applications

Abstract: Redox-active stimuli have gained a great deal of interest as an indicating factor for designing bioresponsive matrices in gene delivery. Hence, a wide range of gene carriers has been designed incorporating the redox-stimuli characteristics. The most important type of gene carriers is the class of redox responsive polymers. Among them, disulfide incorporated redox-responsive poly- ethyleneimine (PEI) and its derivatives, as a result of their outstanding DNA entrapping characteristics and their intrinsic endosomo- lytic activity, have attracted considerable attention in recent studies. The review presents the main developments of the characteristics of PEI derivatives and their applications in gene delivery. It is found that despite the uniquely stated characteristics, the noncleavable structure of conventional PEI (high molecular weight PEI: 25k), which makes it a nondegradable material, as well as the frequent inclusion of positively charged amino groups, which reduces its blood circulation period, render conventional PEI a very toxic mate- rial for gene-delivery applications. The extremely high cellular toxicity of conventional PEI has restricted its administration for real in-vivo physiological media. Recent studies have shown that employing low molecular weight PEI cross-linked by disulfide linkages (SS-PEI) and assembling low molecular weight disulfide linkages PEI (LMW SS-PEI) with bio-detachable anionic groups were two successful approaches for increasing bioavailability of the PEI-based gene carriers, while keeping outstanding cellular transfection. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42096.

3D bioprinting of photocrosslinkable hydrogel constructs

Abstract: Three-dimensional (3D) bioprinting comprises a group of biofabrication technologies for the additive manufacturing of 3D constructs by precisely printing biocompatible materials, cells and biochemicals in predesigned spatial positions. These technologies have been successfully applied to fabricate biodegradable 3D constructs with intricate architectures and heterogeneous composition, assuming a pivotal role in the field of tissue engineering. However, the full implementation of bioprinting strongly depends on the development of novel biomaterials exhibiting fast crosslinking schemes and appropriate printability, cell-compatibility and biomechanical properties. Photocrosslinkable hydrogels are attractive materials for bioprinting as they provide fast polymerization under cell-compatible conditions and exceptional spatiotemporal control over the gelation process. Photopolymerization can also be performed during the bioprinting to promote the instantaneous formation of hydrogel with high well-defined architecture and structural stability. In this review paper, we summarize the most recent developments on bioprinting of photocrosslinkable biodegradable hydrogels for tissue engineering, focusing on the chemical modification strategies and the combination of photocrosslinking reactions with other gelation modalities. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42458.

Fouling control on microfiltration/ultrafiltration membranes: effects of morphology, hydrophilicity, and charge

Abstract: Membrane-based separation processes are very susceptible to flux decline because of concentration polarization and fouling problems. Despite the immense applications of low-pressure driven microfiltration (MF) and ultrafiltration (UF) membranes in various fields, fouling is considered a major negative aspect, and it renders the membrane with a reduced lifetime. The important membrane properties, hydrophilicity, charge, and morphology mainly gained by the membrane during its formation process are considered to be deciding factors in fouling. In this review, we spotlight the effects of the hydrophilicity, charge, and morphology on MF and UF fouling, the principles of the most frequently used instrumentation techniques in predicting these factors, and measures that can be taken for fouling control. The review also focuses on the UF and MF membrane modification techniques used to attain high antifouling characteristics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42042.

Influence of processing conditions on polymorphic behavior, crystallinity, and morphology of electrospun poly(VInylidene fluoride) nanofibers

Abstract: The polymorphism and crystallinity of poly(vinylidene fluoride) (PVDF) membranes, made from electrospinning of the PVDF in pure N,N-dimethylformamide (DMF) and DMF/acetone mixture solutions are studied. Influence of the processing and solu- tion parameters such as flow rate, applied voltage, solvent system, and mixture ratio, on nanofiber morphology, total crystallinity, and crystal phase content of the nanofibers are investigated using scanning electron microscopy, wide-angle X-ray scattering, differen- tial scanning calorimetric, and Fourier transform infrared spectroscopy. The results show that solutions of 20% w/w PVDF in two sol- vent systems of DMF and DMF/acetone (with volume ratios of 3/1 and 1/1) are electrospinnable; however, using DMF/acetone volume ratio of 1/3 led to blockage of the needle and spinning process was stopped. Very high fraction of b-phase (� 79%-85%) was obtained for investigated nanofiber, while degree of crystallinity increased to 59% which is quite high due to the strong influence of electrospinning on ordering the microstructure. Interestingly, ultrafine fibers with the diameter of 12 and 15 nm were obtained in this work. Uniform and bead free nanofiber was formed when a certain amount of acetone was added in to the electrospinning solu- tion. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42304.

Ion-transport study in nanocomposite solid polymer electrolytes based on chitosan: Electrical and dielectric analysis

Abstract: In this study, (1.1111 - x)(0.9CS-0.1NaTf)-xAl(2)O(3)(0.02 <= x <= 0.1) [where CS is chitosan, NaTf is sodium triflate (NaCF3SO3), and Al2O3 is aluminum oxide] nanocomposite solid polymer electrolyte (SPE) films based on CS were prepared by a solution casting technique. X-ray diffraction and scanning electron microscopy analysis revealed that the alumina nanoparticles had a great effect on the structural and morphological behavior of the CS-NaTf (90:10) polymer electrolyte. An investigation of the electrical and dielectric parameters of the nanocomposite SPE films was conducted. Electrical impedance spectroscopy was carried out for this purpose. The relationships between the electrical and dielectric parameters were used to interpret and understand the ion-conduction mechanism. We observed that the direct-current conductivity (sigma(dc)) and dielectric constant followed the same trend with salt concentration. sigma(dc) versus temperature showed the Arrhenius and Vogel-Fulcher-Tammann (VTF) regions. The drops of sigma(dc) at high temperatures were observed for all of the samples. The ion relaxation dynamics were studied from Argand plots. For the first time, we confirmed the existence of a strong experimental relationship between the high-frequency semicircle of the impedance plots and the high-frequency dispersion regions of the alternating-current conductivity (sigma(ac)). The dispersion regions of sigma(ac) were used to study the ion-conduction mechanism. The behavior of the frequency exponent as a function of the temperature was used to interpret sigma(dc) versus the temperature. (C) 2014 Wiley Periodicals, Inc.

Synthesis and characterization of microcrystalline cellulose‐graft‐poly(methyl methacrylate) copolymers and their application as rubber reinforcements

Abstract: In this study, redox-initiated free radical graft copolymerization of microcrystalline cellulose (MCC) and methyl methacrylate (MMA) has been carried out in aqueous media to develop a novel cellulose-based copolymer. Cerium ammonium nitrate was used as the initiator in the presence of nitric acid. Effects of monomer concentration, initiator concentration, polymerization time, and polymerization temperature on the graft parameters of copolymers were studied. The successful grafting copolymerization between MCC and MMA was validated through attenuated total reflection, wide-angle X-ray diffraction, field-emission scanning electron microscopy, and thermal gravimetric analysis. In comparison to native MCC, the resultant copolymers exhibited enhanced thermal stability and better compatibility with natural rubber, suggesting its potential application as reinforcement material in rubber industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42666.

Antibacterial properties of hemp hurd powder against E. coli

Abstract: Hemp (Cannabis sativa L.) is an eco-friendly and multifunctional plant. Hemp hurd is a by-product of hemp plant during hemp fiber separation. Although hemp hurd is repeatedly announced owing antibacterial activity, it has never been systematically investigated and reported. In this study, the antibacterial activity of hemp hurd powder against Escherichia coli is investigated. This article reveals antibacterial activity of hemp hurd where hemp hurd powder inhibits the growth of E. coli. Meanwhile, the self-contamination (forming during retting process) inside hemp hurd has dramatic impact on the antibacterial performance. To achieve better antibacterial activity, hemp hurd was heat treated to eliminate self-contaminations. The impact of the particle sizes and heat treatment on the antibacterial effectiveness was evaluated.

Thiol-norbornene photo-click hydrogels for tissue engineering applications

Abstract: Thiol-norbornene (thiol-ene) photo-click hydrogels have emerged as a diverse material system for tissue engineering applications. These hydrogels are cross-linked through light mediated orthogonal reactions between multi-functional norbornene-modified macromers (e.g., poly(ethylene glycol), hyaluronic acid, gelatin) and sulfhydryl-containing linkers (e.g., dithiothreitol, PEG-dithiol, bis-cysteine peptides) using low concentration of photoinitiator. The gelation of thiol-norbornene hydrogels can be initiated by long-wave UV light or visible light without additional co-initiator or co-monomer. The cross-linking and degradation behaviors of thiol-norbornene hydrogels are controlled through material selections, whereas the biophysical and biochemical properties of the gels are easily and independently tuned owing to the orthogonal reactivity between norbornene and thiol moieties. Uniquely, the cross-linking of step-growth thiol-norbornene hydrogels is not oxygen-inhibited, therefore the gelation is much faster and highly cytocompatible compared with chain-growth polymerized hydrogels using similar gelation conditions. These hydrogels have been prepared as tunable substrates for 2D cell culture, as microgels or bulk gels for affinity-based or protease-sensitive drug delivery, and as scaffolds for 3D cell culture. Reports from different laboratories have demonstrated the broad utility of thiol-norbornene hydrogels in tissue engineering and regenerative medicine applications, including valvular and vascular tissue engineering, liver and pancreas-related tissue engineering, neural regeneration, musculoskeletal (bone and cartilage) tissue regeneration, stem cell culture and differentiation, as well as cancer cell biology. This article provides an up-to-date overview on thiol-norbornene hydrogel cross-linking and degradation mechanisms, tunable material properties, as well as the use of thiol-norbornene hydrogels in drug delivery and tissue engineering applications.

Recent developments in polymers derived from industrial lignin

Abstract: Lignin is an aromatic polymer that makes up 15–30% of the cell walls of terrestrial plants. While lignin's role in facilitating water transport through the vasculature, providing rigidity and acting as a defense against pests and pathogens is important for the plant's survival, industries that process plant biomass for the production of biofuels and bio-based chemicals have historically primarily been interested in the cell wall polysaccharides, especially cellulose. Consequently, lignin is generated in large quantities as a by-product that is often burned to generate heat and electricity, or that is used in low-value applications. It is becoming clear that, rather than treating it as waste, lignin is very suitable for the production of enhanced composites, carbon fibers, and nanomaterials, which offers both economic and environmental benefits. This review highlights recent uses of these polymers as adsorbents, flocculants, adhesives, anti-oxidants, energy storing films, and vehicles for drug delivery and gene therapy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42069.

Fiber preparation and mechanical properties of recycled polypropylene for reinforcing concrete

Abstract: Polypropylene (PP) fibers have been widely used to reinforce concrete footpaths as an alternative to steel mesh. The reinforcing effect of the PP fiber is directly proportional to its tensile strength and Young modulus. This research explored the feasibility of using an improved melt spinning and hot drawing process to produce virgin and recycled PP fibers of high mechanical properties in an industrial scale. Commercial grade granules of virgin PP, recycled PP and HPDE were mixed in different proportions in preparing five different types of fibers. All the fibers obtained high tensile strength and Young modulus. A relationship between the structural parameters and mechanical properties was then established. It was observed that the melt spinning and hot drawing process formed both a-form and b-form crystals in the PP fibers, and significantly improved crystallinity from about 50% to 80%.

Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals

Abstract: Freeze-dried cellulose nanocrystals (CNCs) were dispersed in the thermoplastic polyurethane [Pellethane 2363-55D (P55D)] by a solvent casting method to fabricate CNC-reinforced nanocomposites. This study demonstrated that the addition of small amounts (1-5 wt %) of CNCs to P55D increased the thermal degradation temperature while maintaining a similar stiffness, strength, and elongation of the neat P55D. CNC additions to P55D did not alter the glass-transition temperature, but the onset decomposition temperature was shifted from 286 to 327 degrees C when 1 wt % CNCs was dispersed in the matrix. The higher onset decomposition temperature was attributed to the formation of hydrogen bonds between the hydroxyl groups on the CNC surface and urethane groups in the hard block of P55D. The ultimate tensile strength and strain to failure (epsilon(f)) of the nanocomposites were minimally affected by additions up to 5 wt % CNCs, whereas the elastic modulus was increased by about 70%. The observation that epsilon(f) was unchanged with the addition of up to 5 wt % CNCs suggested that the flow/sliding of the hard blocks and chains were not hindered by the presence of the CNCs during plastic deformation. The ramifications of this study was that CNC additions resulted in wider processing temperatures of P55D for various biomedical devices while maintaining a similar stiffness, strength, and elongation. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41970.

Bio-nanocomposite films based on cellulose nanocrystals filled polyvinyl alcohol/chitosan polymer blend

Abstract: Bio-nanocomposite films based on polyvinyl alcohol/chitosan (PVA/CS) polymeric blend and cellulose nanocrystals (CNC) were prepared by casting a homogenous and stable aqueous mixture of the three components. CNC used as nanoreinforcing agents were extracted at the nanometric scale from sugarcane bagasse via sulfuric acid hydrolysis; then they were characterized and successfully dispersed into a PVA/CS (50/50, w/w) blend to produce PVA/CS-CNC bio-nanocomposite films at different CNC con- tents (0.5, 2.5, 5 wt %). Viscosity measurement of the film-forming solutions and structural and morphological characterizations of the solid films showed that the CNC are well dispersed into PVA/CS blend forming strong interfacial interactions that provide an enhanced load transfer between polymer chains and CNC, thus improving their properties. The obtained bio-nanocomposite films are mechanically strong and exhibit improved thermal properties. The addition of 5 wt % CNC within a PVA/CS blend increased the Young's modulus by 105%, the tensile strength by 77%, and the toughness by 68%. Herein, the utilization of Moroccan sugarcane bagasse as raw material to produce high quality CNC has been explored. Additionally, the ability of the as-isolated CNC to reinforce polymer blends was studied, resulting in the production of the aforementioned bio-nanocomposite films with improved properties. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42004.

Melt processed PLA/PCL blends: Effect of processing method on phase structure, morphology, and mechanical properties

Abstract: Poly(lactic acid) (PLA)-rich poly(lactic acid)/poly(e-caprolactone) (PLA/PCL) blends were melt-blended at different compositions. The compositions such as 90/10 and 80/20 were obtained using three different blending methods and processed by injection molding and hot pressing. All blends were immiscible. The crystallinity of PLA increased slightly in the presence of poly(e-caprolactone) (PCL), and the PCL exhibited fractionated crystallization in the presence of PLA. Injection molded specimens, compared with hot pressed specimens, presented much smaller PCL particles regardless of the blending method used. Some interfacial adhesion was observed in all cases. The stiffness of PLA/PCL blends decreased as the PCL content was increased and was independent of processing. Injection molded specimens showed ductile behavior and broke at elongation values close to 140%, while the elongation at break of the hot pressed specimens was clearly lower, most likely due to the larger size of the PCL particles. Although the impact strength of the blends remained low, it improved by approximately 200% with 30% PCL and by 350% with 40% PCL. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42641.

Oil-spill cleanup: The influence of acetylated curaua fibers on the oil-removal capability of magnetic composites

Abstract: A magnetic resin based on cardanol, furfural, and curaua fibers was prepared and characterized. The material could be used in oil-spill cleanup processes, because of its aromatic/aliphatic balance. The resin was prepared through bulk polycondensation of cardanol and furfural in the presence of curaua fibers and maghemite nanoparticles. Hydrophobicity of the curaua fibers was improved by acetylation, increasing the oil-absorbing capability of the composites. The obtained magnetic composites were studied by Fourier-transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Degree of cure, magnetic force, and oil-removal capability tests were also performed. The results show that the composites possess an elevated cure degree in addition to a considerable magnetic force. The materials exhibit a good oil removal capability in the presence of a magnetic field, which is improved by the use of acetylated curaua. In the best case, the composite filled with maghemite and curaua can remove 12 parts of oil from water. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41732.

Recent advances and migration issues in biodegradable polymers from renewable sources for food packaging

Abstract: In recent years, consumer demand for environmental sustainability and legislative actions has pushed the plastic packaging industry toward biobased plastics. However, despite the advantages related to their ecofriendly nature, the commercial large-scale application of biobased polymers as substitutes for conventional petroleum-derived plastic as packaging materials have been limited up to this point because they show limitations in their processability and material properties performances, especially in terms of their diffusion-barrier properties to small molecules; these are critical for food-contact uses. The main strategies used to overcome these issues involve blending with other biopolymers and/or the addition of other substances, such as microfillers, nanofillers, and plasticizers. In this review, we report on the most recent advances and emerging technologies in food-packaging applications that have potential commercial interest and are based on selected biodegradable polymers from renewable sources. Our particular focus is on issues related to food–packaging interactions and the possible consequent migration of substances. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42597.

Critical update on 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer science

Abstract: 2-Methacryloyloxyethyl phosphorylcholine (MPC) is a custom methacrylate with a zwitterionic phosphorylcholine moiety on the side chain. In the past 25 years, MPC has been used as a building block for a wide range of polymeric biomaterials because of its excellent resistance to nonspecific protein adsorption, cell adhesion, and blood coagulation. Recently, MPC polymers with specific features have been used in bioengineering and nanomedicine. This review focuses on three topics that highlight the latest findings on MPC polymers, that is, specific recognition of C-reactive protein (CRP), cell-membrane-penetration abilities, and lubrication properties. These developments will extend the applications of this biomimetic material from bioinert polymers to biosensing, CRP inhibitors, prodrug carriers, subcellular bioimaging, cell manipulation, and joint replacement. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41766.

Development and oxygen scavenging performance of three‐layer active PET films for food packaging

Abstract: Polymeric active materials represent an innovative food packaging concept that has been introduced to improve the quality of foods and to enhance their shelf life. In this article, the effect of the inclusion of an oxygen scavenger in a polymeric matrix, realizing mul- tilayer active polyester films by coextrusion process, is analyzed. In particular, three layer active films, at different mass ratios of the layers, were produced to form symmetrical "ABA" structures comprising polyethylene terephthalate (PET) with a polymeric oxygen scavenger (OS) as core layer and pure PET as external layers. Oxygen scavenging tests conducted on the multilayer active structures have pointed out the role of the relative layer thickness in controlling the scavenging capacity, the activity time and the oxygen absorption rate. A mod- eling of the scavenging phenomena, which combines a quasi steady-state distribution in the skin layers with a flat profile of O2 content in the active core layer, can explain the experimentally observed oxygen absorption rate at short times. Moreover, steady state oxygen trans- port measurements, performed when the scavenger reactive capacity is exhausted, have shown that the presence of the active phase slightly reduces the O2 permeability, compared with the neat PET. The effect, which progressively increases with the amount of active phase in the film formulation, was related to the different morphological state developed on processing. Finally, preliminary shelf life tests on fresh-cut untreated apples suggest that the developed three layer active films have a significant potential in the shelf-life extension of oxygen sensitive food products. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41465.

Thermoset composites functionalized with carbon nanofiber sheets for EMI shielding

Abstract: Carbon nanofiber sheets were developed through filtering well-dispersed carbon nanofiber (CNF) through filtering well-dispersed aqueous solution of CNF particles with 0.4 μm hydrophilic polycarbonate membrane by the aid of high-pressure air. They were used to functionalize composites by the resin transfer molding method. Their functionalized composites were characterized with scanning electron microscopy (SEM), four-point probes and a vector network analyzer to measure their morphologies, electrical conductivity, and electromagnetic interference (EMI) shielding performance over the frequency range of 8–12 GHz (X band), respectively. Their morphologies show that CNF particles are overlapped and tightly connected with each other in their interconnected networks. The CNF sheets are exposed on the surface, although their networks are partially penetrated by polyester resins. Their electrical conductivity can be 3.0 ± 0.2 Scm−1 or so, much higher by ten orders of magnitude than the reported electrical conductivity of CNF-filled composites. Their EMI shielding effectiveness slightly varies in a range of −30 dB to −35 dB as a function of frequency, much higher than that of most CNF or carbon nanotube–filled composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41873.

Enzyme immobilization onto renewable polymeric matrixes: Past, present, and future trends

Abstract: In this review, we present an overview of the different renewable polymers that are currently being used as matrixes for enzyme immobilization and their properties and of new developments in biocatalysts preparation and applications. Polymers obtained from renewable resources have attracted much attention in recent years because they are environmentally friendly and available in large quantities from natural sources. Different methods for the immobilization of enzymes with these matrixes are reviewed, in particular: (1) binding to a prefabricated biopolymer, (2) entrapment, and (3) crosslinking of enzyme molecules. Emphasis is given to relatively recent developments, such as the use of novel supports, novel entrapment methods and protocols of polymer derivatization, and the crosslinking of enzymes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42125.

Nanoporous membranes generated from self‐assembled block polymer precursors: Quo Vadis?

Abstract: Nanoporous membranes based on self-assembled block polymer precursors are an emerging class of promising separation, purification, and sensing devices due to the ability of researchers to control the nanostructure and chemistry of these multifunctional materials and devices. In fact, modern polymer chemistry provides techniques for the facile, controlled synthesis of the block polymers that constitute these devices. These designer macromolecules, in turn, can then self-assemble into functional nanostructures depending upon the chemical identity of the synthesized block polymers and the thin film fabrication methods employed. After fabrication, these nanoporous membranes offer a highly tunable platform for applications that require high throughput, high surface area, homogeneous pore size, and varying material properties. And, with these readily tunable chemical and structural properties, block polymer membranes will allow for significant improvements in myriad applications. In this Review, we summarize the key advances, with a specific emphasis on the previous 5 years of work, that have allowed block polymer-based membranes to reach their current level of technology. Furthermore, we project how these state-of-art, self-assembled block polymer membrane technologies can be utilized in present-day and future application arenas. In this way, we aim to demonstrate that the rigorous work performed on block polymer-based membranes has laid a strong foundation that will allow these macromolecular systems to: (1) be major avenues of fundamental scientific research and (2) be parlayed into transferable technologies for the betterment of society in the imminent future. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41683.

Impact of Oxygen Transport Properties on Polypropylene Thermal Oxidation, Part 1: Effect of Oxygen Solubility

Abstract: A general kinetic model is proposed to describe the polypropylene thermal oxidation of thin polypropylene films in a wide range of temperatures (from 60 to 200°C) and oxygen partial pressures (from 0.02 to 5 MPa) using a single set of parameters. This model was calibrated with several series of experimental data including analyses of primary (hydroperoxides) and secondary oxidation products (carbonyl species), and subsequent changes in macromolecular properties (average molecular masses). It predicts the experimental data previously published in the literature in terms of induction times and maximal oxidation rates. The variability of the oxygen solubility coefficient allows to explain the scattering of induction times and oxidation rates among the whole iPP family, but also the dependence of this latter quantity with oxygen partial pressure. This variability is presumably due to iPP polymorphism in the temperature range where oxygen permeability is commonly measured. It is concluded that the kinetic model can be used to study the direct effect of iPP morphology on its thermal oxidation kinetics (chemistry of oxidation).

Electrospinning of gelatin fibers using solutions with low acetic acid concentration: effect of solvent composition on both diameter of electrospun fibers and cytotoxicity

Abstract: Gelatin fibers were prepared by electrospinning of gelatin/acetic acid/water ternary mixtures with the aim of studying the feasibility of fabricating gelatin nanofiber mats at room temperature using an alternative benign solvent by significantly reducing the acetic acid concentration. The results showed that gelatin nanofibers can be optimally electrospun with low acetic acid concentration (25%, v/v) combined with gelatin concentrations higher than 300 mg/mL. Both gelatin solutions and electrospun gelatin mats (prepared with different acetic acid aqueous solutions) were analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry techniques to determine the chemical and structural changes of the polymer. The electrospun gelatin mats fabricated from solutions with low acetic acid content showed some advantages as the maintenance of the decomposition temperature of the pure gelatin (∼ 230°C) and the reduction of the acid content on electrospun mats, which allowed to reach a cell viability upper than 90% (analyzed by cell viability test using human dermal fibroblast and embryonic kidney cells). This study has also analyzed the influence of gelatin and acetic acid concentration both on the solution viscosity and the electrospun fiber diameter, obtaining a clear relationship between these parameters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42115.

Genipin-cross-linked chitosan-based hydrogels: Reaction kinetics and structure-related characteristics

Abstract: The main aim of this work is the synthesis and characterization of cross-linked chitosan systems. Chitosan hydrogels can be prepared by physical or chemical cross-linking of polymer chains. Chemical cross-linking, leading to the creation of hydrogel networks possessing improved mechanical properties and chemical stability, can be achieved using either synthetic agents or natural-based agents. In this work, the cross-linker Genipin, a naturally derived compound, was selected because of the lower acute toxicity compared to many other commonly used synthetic cross-linking reagents. In particular, the chemical stabilization of chitosan through genipin cross-linking molecules was performed and characterized by calorimetric analyses (differential scanning calorimetry), swelling measurements in different pHs, and ionic strength. The reaction kinetics was carried out by means of rheological measurements, and both the activation energy (Ea) and the reaction order (m) were calculated. The hydrogel analyses were carried out at different concentrations of genipin (GN1 and GN2). The results were used to evaluate the possibility to use the chemical cross-linked chitosan–genipin hydrogel for biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42256.

Hydrolytic degradation of biodegradable polyesters under simulated environmental conditions

Abstract: In this study, the durability of poly(butylene succinate) (PBS), poly(butylene adipate-co-terephthalate) (PBAT), and PBS/PBAT blend was assessed by exposure to 50°C and 90% relative humidity for a duration of up to 30 days. Due to the easy hydrolysis of esters, the mechanical properties of PBS and PBAT were significantly affected with increasing conditioning time. The PBS, PBAT, and PBS/PBAT showed an increase in modulus as well as a decrease in tensile strength and elongation at break with increased exposure time. Furthermore, the impact strength of PBAT remains unaffected up to 30 days of exposure. However, it was clearly observed that the fracture mode of PBS/PBAT changed from ductile to brittle after being exposed to high heat and humid conditions. This may be attributed to the hydrolysis products of PBS accelerating the degradation of PBAT in the PBS/PBAT blend. The differential scanning calorimetry results suggested that the crystallinity of the samples increased after being exposed to elevated temperature and humidity. This phenomenon was attributed to the induced crystallization from low molecular weight polymer chains that occurred during hydrolysis. Therefore, low molecular weight polymer chains are often favored to the crystallinity enhancement. The increase in crystallinity eventually increased the modulus of the conditioned samples. The enhanced crystallinity was further confirmed by polarizing optical microscopy analysis. Moreover, the hydrolysis of the polyesters was evaluated by scanning electron microscopy, rheology, and Fourier transform infrared spectroscopy analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42189.

A facile dip-coating approach to prepare SiO2/fluoropolymer coating for superhydrophobic and superoleophobic fabrics with self-cleaning property

Abstract: In this study, a facile, two-step dip-coating approach was reported for the fabrication of the superhydrophobic and superoleophobic cotton fabrics. It was confirmed that the superhydrophobic and superoleophobic composite thin film containing modified-SiO2 nanoparticles and fluoropolymer had been successfully fabricated on the cotton fabrics surface, the results demonstrated that the treated cotton fabrics showed good performances, such as superhydrophobicity and superoleophobicity, low water and oil absorption ability, self-cleaning property and good laundering durability, so forth. The above approach can be applied to potentially advance superhydrophobic and superoleophobic fabrics materials for a variety of applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41458.

Making polymeric membranes antifouling via “grafting from” polymerization of zwitterions

Abstract: Protein-fouling of membranes has negative effects on the wide applications of membrane materials, such as poly(vinylidene fluoride) (PVDF), poly(ether sulfone) (PES)/polysulfone (PSf). Zwitterionic materials have recently been used and identified from high throughput screens of large libraries of monomers to modify membranes due to their stable anti-protein-fouling properties. “Grafting from” polymerization is a technique involving monomers that are polymerized using an initiation reaction on the membrane surface. It is regarded as a simple, useful, and versatile modification approach to increase the anti-fouling properties of a membrane. This strategy provides controllable introduction of graft chains with a high density and a long-term chemical stability due to covalent attachment of graft chains. Graft density, chemistry, chain length, and conformation are all important parameters that need to be considered. This article presents a mini-review of recent progress on the “grafting from” polymerization of zwitterionic monomers on the surfaces of PVDF and PES/PSf membranes, including an introduction of zwitterions and methods of graft polymerization. Various approaches such as free radical graft polymerization, photo-induced graft polymerization, and plasma-induced graft polymerization were compared based on uniformity and amount of grafted zwitterionic polymer, relative flux of modified membranes, simplicity and environment pollution of operation, and cost of technique. The application of different approaches and the performance of poly(zwitterion)-grafted PVDF and PES/PSf membranes are summarized according to recent research. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41781.