text: Polymers http://www.mdpi.com/journal/polymers Latest open access articles published in Polymers at http://www.mdpi.com/journal/polymers http://www.mdpi.com/2073-4360/7/4/629 Electrospun nanofiber membranes have been extensively studied as separators in Li-ion batteries due to their large porosity, unique pore structure, and high electrolyte uptake. However, the electrospinning process has some serious drawbacks, such as low spinning rate and high production cost. The centrifugal spinning technique can be used as a fast, cost-effective and safe technique to fabricate high-performance fiber-based separators. In this work, polymethylmethacrylate (PMMA)/polyacrylonitrile (PAN) membranes with different blend ratios were produced via centrifugal spinning and characterized by using different electrochemical techniques for use as separators in Li-ion batteries. Compared with commercial microporous polyolefin membrane, centrifugally-spun PMMA/PAN membranes had larger ionic conductivity, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. Centrifugally-spun PMMA/PAN membrane separators were assembled into Li/LiFePO4 cells and these cells delivered high capacities and exhibited good cycling performance at room temperature. In addition, cells using centrifugally-spun PMMA/PAN membrane separators showed superior C-rate performance compared to those using microporous polypropylene (PP) membranes. It is, therefore, demonstrated that centrifugally-spun PMMA/PAN membranes are promising separator candidate for high-performance Li-ion batteries. Polymers 2015-04-01 7 4 Article 10.3390/polym7040629 629 643 2073-4360 2015-04-01 doi: 10.3390/polym7040629 Meltem Yanilmaz Xiangwu Zhang http://www.mdpi.com/2073-4360/7/4/610 In a previous work, we described a multi-scale protocol for the simulation of the conformation and dynamics of macromolecules that was applied to dendrimer molecules proving its predictive capability by comparison with experimental data. That scheme is now employed in order to predict conformational properties (radius of gyration) and overall hydrodynamic properties (translational diffusion and intrinsic viscosity) of hyperbranched molecules in dilute solution. For that purpose, we use a very simple coarse-grained bead-and-spring model whose parameters are not adjusted against experimental properties but they are obtained from previous atomic-level (Langevin) simulations of small fragments of real hyperbranched polymers. In addition, we devise a method to generate structures with different degree of branching. The Monte Carlo simulation technique was used to generate the set conformations of the coarse-grained model. In spite of the difficulties of reproducing experimental data of highly polydisperse entities (in terms of both molecular weight and topology) without using adjustable parameters, the results of this paper show that the proposed methodology allows for qualitative predictions of the behavior of such complex systems and lead us to conclude that, after some improvement, acceptable quantitative predictions can be achieved. Polymers 2015-03-30 7 4 Article 10.3390/polym7040610 610 628 2073-4360 2015-03-30 doi: 10.3390/polym7040610 Ricardo Schmidt José Hernández Cifre José de la Torre http://www.mdpi.com/2073-4360/7/4/592 The integration of block copolymer (BCP) self-assembled nanopattern formation as an alternative lithographic tool for nanoelectronic device fabrication faces a number of challenges such as defect densities, feature size, pattern transfer, etc. Key barriers are the nanopattern process times and pattern formation on current substrate stack layers such as hard masks (e.g., silicon nitride, Si3N4). We report a rapid microwave assisted solvothermal (in toluene environments) self-assembly and directed self-assembly of a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP thin films on planar and topographically patterned Si3N4 substrates. Hexagonally arranged, cylindrical structures were obtained and good pattern ordering was achieved. Factors affecting BCP self-assembly, notably anneal time and temperature, were studied and seen to have significant effects. Graphoepitaxy within the topographical structures provided long range, translational alignment of the patterns. The effect of surface topography feature size and spacing was investigated. The solvothermal microwave based technique used to provide periodic order in the BCP patterns showed significant promise and ordering was achieved in much shorter periods than more conventional thermal and solvent annealing methods. The implications of the work in terms of manufacturing technologies are discussed. Polymers 2015-03-30 7 4 Article 10.3390/polym7040592 592 609 2073-4360 2015-03-30 doi: 10.3390/polym7040592 Dipu Borah Sozaraj Rasappa Ramsankar Senthamaraikannan Justin Holmes Michael Morris http://www.mdpi.com/2073-4360/7/3/580 Feather keratin (FK) extracted from feathers represents a valuable source of biodegradable and biocompatible polymer. The aim of this study was the development and characterization of blended films based on FK and polyvinyl alcohol (PVA) cross-linked by dialdehyde starch (DAS) for a potential drug release application. The compatibility of FK/PVA was improved when cross-linked by DAS: the relative crystallinity of the PVA/FK film slightly decreased, and the enthalpy value for the melting peak decreased by about 50% for the cross-linked films. The total soluble mass of all blend films in water was below 35% at 37 °C, indicating a good stability of the films in water. The results of the Rhodamine B dye (as a model drug) release tests showed that the release rates decreased with increasing DAS content. DAS-induced cross-linking improves several important properties of the FK/PVA films, such as the compactness, the compatibility, and the stability in water. These improvements offer the potential to expand the application of FK films in the biomaterial field. Polymers 2015-03-23 7 3 Article 10.3390/polym7030580 580 591 2073-4360 2015-03-23 doi: 10.3390/polym7030580 Yao Dou Buning Zhang Ming He Guoqiang Yin Yingde Cui Irina Savina http://www.mdpi.com/2073-4360/7/3/552 Chitosan is a unique biopolymer in the respect that it is abundant, cationic, low-toxic, non-immunogenic and biodegradable. The relative occurrence of the two monomeric building units (N-acetyl-glucosamine and d-glucosamine) is crucial to whether chitosan is predominantly an ampholyte or predominantly a polyelectrolyte at acidic pH-values. The chemical composition is not only crucial to its surface activity properties, but also to whether and why chitosan can undergo a sol–gel transition. This review gives an overview of chitosan hydrogels and their biomedical applications, e.g., in tissue engineering and drug delivery, as well as the chitosan's surface activity and its role in emulsion formation, stabilization and destabilization. Previously unpublished original data where chitosan acts as an emulsifier and flocculant are presented and discussed, showing that highly-acetylated chitosans can act both as an emulsifier and as a flocculant. Polymers 2015-03-13 7 3 Review 10.3390/polym7030552 552 579 2073-4360 2015-03-13 doi: 10.3390/polym7030552 Julie Nilsen-Nygaard Sabina Strand Kjell Vårum Kurt Draget Catherine Nordgård http://www.mdpi.com/2073-4360/7/3/527 In the present study, silane-functionalized graphene (f-graphene)-reinforced chitosan nanocomposite films exhibiting enhanced mechanical properties have been prepared by the solution casting method. These nanocomposite films were characterized by X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. In order to investigate the effect of silane functionalization, tensile tests were performed on original, oxidized and silane-functionalized graphene-reinforced chitosan nanocomposite films. Tensile results show that silane functionalization groups offer a substantial increase in the interfacial adhesion between filler and host matrix. This result is also confirmed by the surface morphology of the fracture surface in scanning electron microscope analysis. Qualitative analysis using Raman and Fourier transform infrared spectroscopy revealed the existence of Si–O–Si and Si–O–C bonds in the silanized composite. Thermal analysis of the samples shows that the material is stable up till 250 °C and maintains its thermal stability all throughout the process until it starts degrading after 510 °C. Atomic force microscopy reveals that the material is well exfoliated after the oxidation of graphene and also displays the existence of 3–6 layers of exfoliated graphene sheets. X-ray photoelectron spectroscopy studies also reveal the existence of silicon in the single state and quantify the sample to be approximately around 4% (±0.5%) of the total atomic weight. Polymers 2015-03-13 7 3 Article 10.3390/polym7030527 527 551 2073-4360 2015-03-13 doi: 10.3390/polym7030527 Dae Kim Vivek Dhand Kyong Rhee Soo-Jin Park http://www.mdpi.com/2073-4360/7/3/504 The latest techniques used to prove, describe and analyze the gas phase activity of a fire retardant used in polymeric materials are briefly reviewed. Classical techniques, such as thermogravimetric analysis or microscale combustion calorimetry, as well as complex and advanced analytical techniques, such as modified microscale combustion calorimeter (MCC), molecular beam mass spectroscopy and vacuum ultra violet (VUV) photoionization spectroscopy coupled with time of flight MS (TOF-MS), are described in this review. The recent advances in analytical techniques help not only in determining the gas phase activity of the flame-retardants but also identify possible reactive species responsible for gas phase flame inhibition. The complete understanding of the decomposition pathways and the flame retardant activity of a flame retardant system is essential for the development of new eco-friendly-tailored flame retardant molecules with high flame retardant efficiency. Polymers 2015-03-10 7 3 Review 10.3390/polym7030504 504 526 2073-4360 2015-03-10 doi: 10.3390/polym7030504 Khalifah Salmeia Julien Fage Shuyu Liang Sabyasachi Gaan http://www.mdpi.com/2073-4360/7/3/484 Two types of reversible addition-fragmentation chain transfer molecularly imprinted polymers (RAFT-MIPs) were synthesized using different monomers, which were methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) and 2-hydroxyethyl methacrylate functionalized β-cyclodextrin (HEMA-β-CD), via reversible addition-fragmentation chain transfer (RAFT) polymerization, and were represented as RAFT-MIP(MAA-β-CD) and RAFT-MIP(HEMA-β-CD), respectively. Both RAFT-MIPs were systematically characterized using Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Brunauer-Emmett-Teller (BET), and rebinding experimental study. The results were compared with MIPs synthesized via the traditional radical polymerization (TRP) process, and were represented as MIP(MAA-β-CD) and MIP(HEMA-β-CD). Morphology results show that RAFT-MIP(MAA-β-CD) has a slightly spherical feature with a sponge-like form, while RAFT-MIP(HEMA-β-CD) has a compact surface. BET results show that the surface area of RAFT-MIP(MAA-β-CD) is higher than MIP(MAA-β-CD), while the RAFT-MIP(HEMA-β-CD) surface area is lower than that of MIP(HEMA-β-CD). Rebinding experiments indicate that the RAFT agent increased the binding capacity of RAFT-MIP(MAA-β-CD), but not of RAFT-MIP(HEMA-β-CD), which proves that a RAFT agent does not always improve the recognition affinity and selective adsorption of MIPs. The usability of a RAFT agent depends on the monomer used to generate potential MIPs. Polymers 2015-03-06 7 3 Article 10.3390/polym7030484 484 503 2073-4360 2015-03-06 doi: 10.3390/polym7030484 Saliza Asman Sharifah Mohamad Norazilawati Sarih http://www.mdpi.com/2073-4360/7/3/468 Novel bio-based aliphatic copolyesters, poly(lactic acid-co-10-hydroxy decanoate) (P(LA-co-HDA), PLH), were successfully synthesized from lactic acid (LA) and 10-hydroxycapric acid (HDA) by a thermal polycondensation process, in the presence of p-toluenesulfonic acid (p-TSA) and SnCl2·2H2O as co-catalyst. The copolymer structure was characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR). The weight average molecular weights (Mw) of PLH, from gel permeation chromatography (GPC) measurements, were controlled from 18,500 to 37,900 by changing the molar ratios of LA and HDA. Thermogravimetric analysis (TGA) results showed that PLH had excellent thermal stability, and the decomposition temperature at the maximum rate was above 280 °C. The glass transition temperature (Tg) and melting temperature (Tm) of PLH decreased continuously with increasing the HDA composition by differential scanning calorimetry (DSC) measurements. PLH showed high ductility, and the breaking elongation increased significantly by the increment of the HDA composition. Moreover, the PLH copolymer could degrade in buffer solution. The cell adhesion results showed that PLH had good biocompatibility with NIH/3T3 cells. The bio-based PLH copolymers have potential applications as thermoplastics, elastomers or impact modifiers in the biomedical, industrial and agricultural fields. Polymers 2015-03-05 7 3 Article 10.3390/polym7030468 468 483 2073-4360 2015-03-05 doi: 10.3390/polym7030468 Dongjian Shi Jinting Hua Li Zhang Mingqing Chen http://www.mdpi.com/2073-4360/7/3/453 As a part of our continuing work to improve the flame retardance of some chain-growth polymers, by employing a reactive route, we have synthesized several unsaturated compounds containing either phosphorus (P), or both phosphorus (P) and nitrogen (N), bearing groups in different chemical environments. They included: diethyl(acryloyloxymethyl)phosphonate (DEAMP); diethyl(1-acryloyloxyethyl)phosphonate (DE1AEP); diethyl-2-(acryloyloxy)ethyl phosphate (DEAEP); diethyl-2-(metharyloyloxy)ethyl phosphate (DEMEP); acrylic acid-2-(diethoxyphosphorylamino)ethyl ester (ADEPAE); acrylic acid-2-[(diethoxyphosphoryl)methyl amino]ethyl ester (ADEPMAE). Acrylonitrile (AN), methyl methacrylate (MMA) and styrene (S) were free radically copolymerised with the above mentioned comonomers. The recovered polymers were subjected to routine spectroscopic and thermo-gravimetric analyses. In addition, the combustion behaviours of homopolymers as well as the copolymers containing nominal loadings of P-, or P/N-, groups were, primarily, evaluated using pyrolysis combustion flow calorimetry (PCFC). PCFC has been found to be a very useful screening technique, especially, in establishing the efficacies of the different modifying groups towards flame retarding some base polymeric materials. Values of the heat release capacity (HRC) values normalised to the P contents (wt%) can be considered as useful tool in ranking the various P-containing modifying groups in terms of their efficacies to flame-retard non-halogenated chain-growth polymers considered in the present work. Polymers 2015-03-02 7 3 Article 10.3390/polym7030453 453 467 2073-4360 2015-03-02 doi: 10.3390/polym7030453 Svetlana Tretsiakova-McNally Paul Joseph http://www.mdpi.com/2073-4360/7/3/418 A systematic investigation into the chain transfer polymerization of the so-called radical precursor polymerization of poly(p-phenylene vinylene) (PPV) materials is presented. Polymerizations are characterized by systematic variation of chain transfer agent (CTA) concentration and reaction temperature. For the chain transfer constant, a negative activation energy of −12.8 kJ·mol−1 was deduced. Good control over molecular weight is achieved for both the sulfinyl and the dithiocarbamate route (DTC). PPVs with molecular weights ranging from thousands to ten thousands g·mol−1 were obtained. To allow for a meaningful analysis of the CTA influence, Mark–Houwink–Kuhn–Sakurada (MHKS) parameters were determined for conjugated MDMO-PPV ([2-methoxy-5-(3',7'-dimethyloctyloxy)]-1,4-phenylenevinylene) to α = 0.809 and k = 0.00002 mL·g−1. Further, high-endgroup fidelity of the CBr4-derived PPVs was proven via chain extension experiments. MDMO-PPV-Br was successfully used as macroinitiator in atom transfer radical polymerization (ATRP) with acrylates and styrene. A more polar PPV counterpart was chain extended by an acrylate in single-electron transfer living radical polymerization (SET-LRP). In a last step, copper-catalyzed azide alkyne cycloaddition (CuAAC) was used to synthesize block copolymer structures. Direct azidation followed by macromolecular conjugation showed only partial success, while the successive chain extension via ATRP followed by CuAAC afforded triblock copolymers of the poly(p-phenylene vinylene)-block-poly(tert-butyl acrylate)-block-poly(ethylene glycol) (PPV-b-PtBuA-b-PEG). Polymers 2015-02-24 7 3 Article 10.3390/polym7030418 418 452 2073-4360 2015-02-24 doi: 10.3390/polym7030418 Neomy Zaquen Joke Vandenbergh Maria Schneider-Baumann Laurence Lutsen Dirk Vanderzande Thomas Junkers http://www.mdpi.com/2073-4360/7/3/390 Detailed atomistic (united atoms) molecular dynamics simulations of several graphene based polymer (polyethylene, PE) nanocomposite systems have been performed. Systems with graphene sheets of different sizes have been simulated at the same graphene concentration (~3%). In addition, a periodic graphene layer ("infinite sheet") has been studied. Results concerning structural and dynamical properties of PE chains are presented for the various systems and compared to data from a corresponding bulk system. The final properties of the material are the result of a complex effect of the graphene's sheet size, mobility and fluctuations. A detailed investigation of density, structure and dynamics of the hybrid systems has been conducted. Particular emphasis has been given in spatial heterogeneities due to the PE/graphene interfaces, which were studied through a detailed analysis based on radial distances form the graphene's center-of-mass. Chain segmental dynamics is found to be slower, compared to the bulk one, at the PE/graphene interface by a factor of 5 to 10. Furthermore, an analysis on the graphene sheets characteristics is presented in terms of conformational properties (i.e., wrinkling) and mobility. Polymers 2015-02-23 7 3 Article 10.3390/polym7030390 390 417 2073-4360 2015-02-23 doi: 10.3390/polym7030390 Anastassia Rissanou Albert Power Vagelis Harmandaris http://www.mdpi.com/2073-4360/7/3/373 The current paper focuses on the preparation and some characteristics of viscoelastic hydrogels, ViscoGels™, made from chitosans having a random acylation pattern. Three different chitosan batches with a high fraction of acetylation were selected based on their Mw, and the impact of degree of cross-linking on these chitosan samples has been studied with respect to the properties of the final hydrogels. Rheological long term (12 month) stability and gelling kinetics data are presented together with results from swelling studies at different pH. Finally, an example illustrating these gels potential as drug delivery vehicles is presented and discussed. Polymers 2015-02-18 7 3 Article 10.3390/polym7030373 373 389 2073-4360 2015-02-18 doi: 10.3390/polym7030373 Henry Franzén Kurt Draget Joakim Langebäck Julie Nilsen-Nygaard http://www.mdpi.com/2073-4360/7/2/333 Improving power conversion efficiency and device performance stability is the most critical challenge in polymer solar cells for fulfilling their applications in industry at large scale. Various methodologies have been developed for realizing this goal, among them interfacial layer engineering has shown great success, which can optimize the electrical contacts between active layers and electrodes and lead to enhanced charge transport and collection. Interfacial layers also show profound impacts on light absorption and optical distribution of solar irradiation in the active layer and film morphology of the subsequently deposited active layer due to the accompanied surface energy change. Interfacial layer engineering enables the use of high work function metal electrodes without sacrificing device performance, which in combination with the favored kinetic barriers against water and oxygen penetration leads to polymer solar cells with enhanced performance stability. This review provides an overview of the recent progress of different types of interfacial layer materials, including polymers, small molecules, graphene oxides, fullerene derivatives, and metal oxides. Device performance enhancement of the resulting solar cells will be elucidated and the function and operation mechanism of the interfacial layers will be discussed. Polymers 2015-02-17 7 2 Review 10.3390/polym7020333 333 372 2073-4360 2015-02-17 doi: 10.3390/polym7020333 Hao Zeng Xucheng Zhu Yongye Liang Xugang Guo http://www.mdpi.com/2073-4360/7/2/316 Polyamide 6 (PA6) is a widely-used polymer that could find applications in various sectors, including home textiles, transportation or construction. However, due to its organic nature, PA6 is flammable, and flame-retardant formulations have to be developed to comply with fire safety standards. Recently, it was proposed to use ammonium sulfamate as an effective flame retardant for PA6, even at low loading content. However, processing issues could occur with this additive considering large-scale production. This paper thus studies the use of another sulfamate salt—guanidine sulfamate (GAS)—and evidences its high efficiency when combined with melamine polyphosphate (MPP) as a flame retardant for PA6. A decrease of the peak of the heat release rate by 30% compared to pure PA6 was obtained using only 5 wt% of a GAS/MPP mixture in a microscale calorimeter. Moreover, PA6 containing the mixture GAS/MPP exhibits a Limiting Oxygen Index (LOI) of 37 vol% and is rated V0 for the UL 94 test (Vertical Burning Test; ASTM D 3801). The mechanisms of degradation were investigated analyzing the gas phase and solid phase when the material degrades. It was proposed that MPP and GAS modify the degradation pathway of PA6, leading to the formation of nitrile end-group-containing molecules. Moreover, the formation of a polyaromatic structure by the reaction of MPP and PA6 was also shown. Polymers 2015-02-13 7 2 Article 10.3390/polym7020316 316 332 2073-4360 2015-02-13 doi: 10.3390/polym7020316 Mathieu Coquelle Sophie Duquesne Mathilde Casetta Jun Sun Xiaoyu Gu Sheng Zhang Serge Bourbigot http://www.mdpi.com/2073-4360/7/2/298 Novel blends of two furan resins with an unsaturated polyester have been prepared and cured by parallel free radical (for the unsaturated polyester) and acid-catalysed crosslinking (for the furan resin) to give co-cured composite materials. Although these materials have inferior physical properties, such as low Tg and low storage modulus compared with those of unsaturated polyester and furan resins alone, they show markedly improved flame retardance compared with that of the normally highly flammable unsaturated polyester. This increased flame retardance arises from a condensed phase mechanism in which the furanic component forms a semi-protective char, reducing rates of thermal degradation and total heat release and heat of combustion. The blends also burn with reduced smoke output compared with that from unsaturated polyester alone. Polymers 2015-02-11 7 2 Article 10.3390/polym7020298 298 315 2073-4360 2015-02-11 doi: 10.3390/polym7020298 Baljinder Kandola John Ebdon Kawser Chowdhury http://www.mdpi.com/2073-4360/7/2/281 The basement membrane, a thin extracellular matrix, plays a critical role in tissue development and repair. Laminins are the major component of basement membrane and have diverse biological activities. We have identified various cell-adhesive peptides from laminins and their specific cell surface receptors. Polysaccharides, including chitosan, have been used as scaffolds, which regulate cellular functions for tissue engineering. We have developed laminin-derived active peptide-chitosan matrices as functional scaffolds. The biological activity of the peptides was enhanced when the peptides were conjugated to a chitosan matrix, suggesting that the peptide-chitosan matrix approach has an advantage for an active biomaterial. Further, the laminin peptide-chitosan matrices have the potential to mimic the basement membrane and are useful for tissue engineering as an artificial basement membrane. Polymers 2015-02-11 7 2 Review 10.3390/polym7020281 281 297 2073-4360 2015-02-11 doi: 10.3390/polym7020281 Kentaro Hozumi Jun Kumai Yuji Yamada Motoyoshi Nomizu http://www.mdpi.com/2073-4360/7/2/266 Polymer electrolytes based on 90 wt% of methyl methacrylate and 10 wt% of ethyl methacrylate (90MMA-co-10EMA) incorporating different weight ratios of sodium iodide were prepared using the solution casting method. The complexation between salt and copolymer host has been investigated using Fourier transform infrared spectroscopy. The ionic conductivity and thermal stability of the electrolytes were measured using impedance spectroscopy and differential scanning calorimetry, respectively. Scanning electron microscopy was used to study the morphology of the polymer electrolytes. The ionic conductivity and glass transition temperature increased up to 20 wt% of sodium iodide (5.19 × 10−6 S·cm−1) and decreased with the further addition of salt concentration, because of the crosslinked effect. The morphology behavior of the highest conducting sample also showed smaller pores compared to the other concentration. The total ionic transference number proved that this system was mainly due to ions, and the electrochemical stability window was up to 2.5 V, which is suitable for a dye-sensitized solar cell application. This sample was then tested in a dye-sensitized solar cell and exhibited an efficiency of 0.62%. Polymers 2015-02-09 7 2 Article 10.3390/polym7020266 266 280 2073-4360 2015-02-09 doi: 10.3390/polym7020266 Nurul Dzulkurnain Azizan Ahmad Nor Mohamed http://www.mdpi.com/2073-4360/7/2/235 In this mini-review, we shall first cover a short history of the discovery of chitin isolated from sponges; as well as its evolutionarily ancient roots. Next, we will delve into the unique structural, mechanical, and thermal properties of this naturally occurring polymer to illuminate how its physicochemical properties may find uses in diverse areas of the material sciences. We show how the unique properties and morphology of sponge chitin renders it quite useful for the new route of "Extreme Biomimetics"; where high temperatures and pressures allow a range of interesting bioinorganic composite materials to be made. These new biomaterials have electrical, chemical, and material properties that have applications in water filtration, medicine, catalysis, and biosensing. Polymers 2015-02-09 7 2 Review 10.3390/polym7020235 235 265 2073-4360 2015-02-09 doi: 10.3390/polym7020235 Marcin Wysokowski Iaroslav Petrenko Allison Stelling Dawid Stawski Teofil Jesionowski Hermann Ehrlich http://www.mdpi.com/2073-4360/7/2/220 The efficiency of new phosphinates, in combination with melamine cyanurate, was studied using different polypropylene textile structures. The influence of different ratios up to a total amount of 6 wt% in the polypropylene fiber was investigated using the limiting oxygen index (LOI) and cone calorimeter method for research purposes, while the performances were correlated to the standards FMVSS 302 (Federal Motor Vehicle Safety Standards) and DIN 4102-l (Deutsches Institut für Normung) used more specifically for automotive and building sector. Polymers 2015-02-09 7 2 Article 10.3390/polym7020220 220 234 2073-4360 2015-02-09 doi: 10.3390/polym7020220 François Rault Stéphane Giraud Fabien Salaün Xavier Almeras http://www.mdpi.com/2073-4360/7/2/186 One-dimensional (1-D) nanostructures have attracted enormous research interest due to their unique physicochemical properties and wide application potential. These 1-D nanofibers are being increasingly applied to biomedical fields owing to their high surface area-to-volume ratio, high porosity, and the ease of tuning their structures, functionalities, and properties. Many biomedical nanofiber reviews have focused on tissue engineering and drug delivery applications but have very rarely discussed their use as wound dressings. However, nanofibers have enormous potential as wound dressings and other clinical applications that could have wide impacts on the treatment of wounds. Herein, the authors review the main fabrication methods of nanofibers as well as requirements, strategies, and recent applications of nanofibers, and provide perspectives of the challenges and opportunities that face multifunctional nanofibers for active therapeutic applications. Polymers 2015-02-03 7 2 Review 10.3390/polym7020186 186 219 2073-4360 2015-02-03 doi: 10.3390/polym7020186 Jaishri Sharma Monira Lizu Mark Stewart Kyle Zygula Yang Lu Rajat Chauhan Xingru Yan Zhanhu Guo Evan Wujcik Suying Wei http://www.mdpi.com/2073-4360/7/2/161 Aqueous chitosan possesses attractive interaction capacities with various molecular groups that can be involved in hydrogen bonds and electrostatic and hydrophobic interactions. In the present paper, we report on the direct determination of chitosan–mucin molecular pair interactions at various solvent conditions as compared to alginate–mucin interactions. Two chitosans of high molecular weight with different degrees of acetylation—thus possessing different solubility profiles in aqueous solution as a function of pH and two alginates with different fractions of α-guluronic acid were employed. The interaction properties were determined through a direct unbinding assay at the single-molecular pair level using an atomic force microscope. When probed against immobilized mucin, both chitosans and alginates revealed unbinding profiles characteristic of localized interactions along the polymers. The interaction capacities and estimated parameters of the energy landscapes of the pairwise chitosan–mucin and alginate–mucin interactions are discussed in view of possible contributions from various fundamental forces. Signatures arising both from an electrostatic mechanism and hydrophobic interaction are identified in the chitosan–mucin interaction properties. The molecular nature of the observed chitosan–mucin and alginate–mucin interactions indicates that force spectroscopy provides fundamental insights that can be useful in understanding the surface binding properties of other potentially mucoadhesive polymers. Polymers 2015-01-29 7 2 Article 10.3390/polym7020161 161 185 2073-4360 2015-01-29 doi: 10.3390/polym7020161 Kristin Haugstad Armend Håti Catherine Nordgård Patricia Adl Gjertrud Maurstad Marit Sletmoen Kurt Draget Rita Dias Bjørn Stokke http://www.mdpi.com/2073-4360/7/1/156 Polymers is instituting an annual award to recognize the outstanding papers in the area of polymer science published in Polymers. We are pleased to announce the second "Polymers Best Paper Award" for 2015 [1]. Nominations were selected by the Editor-in-Chief and Editorial Board members of Polymers from all papers published in 2011. The awards are issued to reviews and articles respectively. We are pleased to announce that the following five papers were chosen:[...] Polymers 2015-01-20 7 1 Editorial 10.3390/polym7010156 156 160 2073-4360 2015-01-20 doi: 10.3390/polym7010156 Alexander Böker http://www.mdpi.com/2073-4360/7/1/147 A new chiral compound was synthesized based on L-borneol. A cholesteric liquid crystal (LC) electrolyte solution was prepared by adding it as a chiral inducer to a nematic LC. A chiral poly(3,4-ethylenedioxythiophene) (PEDOT*, * = asymmetry) film was prepared by electrochemical polymerization in the induced cholesteric LC. The PEDOT* film showed a maximum absorption band due to a π–π* transition in the UV-vis absorption and bisignate Cotton effect in the reduced state in circular dichroism (CD). The CD spectrum indicates that PEDOT* backbones form right-handed helical aggregation. However, the maximum optical absorption band due to π–π* transition of the PEDOT* decreases and a new absorption band appears at long wavelengths upon oxidation due to generation of polarons as charge carriers. Bisignate Cotton effect disappears and broadly negative CD signal appears at long wavelengths in the oxidized state. Polymers 2015-01-20 7 1 Communication 10.3390/polym7010147 147 155 2073-4360 2015-01-20 doi: 10.3390/polym7010147 Atsushi Matsumura Fan Yang Hiromasa Goto http://www.mdpi.com/2073-4360/7/1/134 Novel thermo-responsive elastin-like oligopeptides containing cell-binding epitope (Arg-Gly-Asp-Ser sequence); arginine-glycine-aspartic acid-serine (RGDS)-elastin-like peptides (ELP) and RGDS-deg-ELP; were newly prepared as building blocks of self-assembled molecular layer for artificial extra cellular matrix. A detailed analysis of the conformation of the oligo(ELP)s in water and their self-assembling behavior onto hydrophobic surfaces were performed by using circular dichroism, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy and water contact angle measurements. The experimental results revealed that both oligo(ELP)s self-assembled onto hydrophobic surfaces and formed molecular layers based on their thermo-responsive conformational change from hydrous random coil to dehydrated β-turn structure. Effective cell adhesion and spreading behaviors were observed on these self-assembled oligo(ELP) layers. In addition, attached cells were found to be recovered successfully as a cell-sheet by temperature-induced disassembly of oligo(ELP) layer. This achievement provides an important insight to construct novel oligopeptide-based nano-surfaces for the design of smart artificial extra-cellular matrix. Polymers 2015-01-19 7 1 Article 10.3390/polym7010134 134 146 2073-4360 2015-01-19 doi: 10.3390/polym7010134 Tomoyuki Koga Kazuhiro Nakamoto Koji Odawara Tomoo Matsuoka Nobuyuki Higashi http://www.mdpi.com/2073-4360/7/1/120 In this paper, the self-assembly process of diblock copolymers confined in multi-walled cylindrical nanotubes is systematically investigated using a molecular dynamics (MD) method. The dependence of resultant morphologies on the degree of confinement and on the interaction strength between nanotubes and copolymers is studied comprehensively. When the wall surfaces are not preferential, results indicate that geometric confinement significantly influences copolymer conformations. In addition, the thickness of the helical lamellar structure increases with interaction strength and confinement size. In cases where the nanotubes are strongly attracted to one copolymer block, the confinement effect weakens as geometric space increases. Findings explain the dependence of chain conformation on the degree of confinement and the strength of surface preferences. Polymers 2015-01-16 7 1 Article 10.3390/polym7010120 120 133 2073-4360 2015-01-16 doi: 10.3390/polym7010120 Yuxin Zuo Guoqiang Wang Ying Yu Chuncheng Zuo Luyou Shi Fulei Shi Jie Wei http://www.mdpi.com/2073-4360/7/1/115 The editors of Polymers would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Polymers 2015-01-07 7 1 Editorial 10.3390/polym7010115 115 119 2073-4360 2015-01-07 doi: 10.3390/polym7010115 Polymers Editorial Office http://www.mdpi.com/2073-4360/7/1/91 Protein-based and other hydrophilic thin films are promising materials for the manufacture of edible food packaging and other food and non-food applications. Calcium caseinate (CaCas) films are highly hygroscopic and physical characterization under broad environmental conditions is critical to application development and film optimization. A new technology, humidity-controlled dynamic mechanical analysis (DMA-RH) was explored to characterize CaCas/glycerol films (3:1 ratio) during isohume temperature (T) ramps and steps, and isothermal RH ramps and steps, to determine their mechanical and moisture-sorption properties during extensive T and RH variations. When RH and/or T increased, CaCas/Gly films became strongly plasticized and underwent several primary and secondary humidity-dependent transition temperatures (or transition humidities); the CaCas/Gly network hypothetically rearranged itself to adapt to the increased water-content and heat-induced molecular mobility. Between 5–40 °C and 20%–61% RH, moisture-sorption was rapid and proportional to humidity between transition points and accelerated greatly during transitions. CaCas/Gly films seemed unsuitable for storage or utilization in warm/humid conditions as they lost their mechanical integrity around Tm ~ 40 °C at 50% RH and Tm decreased greatly with increased RH. However, below Tm, both moisture- and heat-induced structural changes in the films were fully reversible and casein films may withstand a variety of moderate abuse conditions. Polymers 2015-01-06 7 1 Article 10.3390/polym7010091 91 114 2073-4360 2015-01-06 doi: 10.3390/polym7010091 Laetitia Bonnaillie Peggy Tomasula http://www.mdpi.com/2073-4360/7/1/69 A strategy that is often used for designing low band gap polymers involves the incorporation of electron-rich (donor) and electron-deficient (acceptor) conjugated segments within the polymer backbone. In this paper we investigate such a series of Diketopyrrolopyrrole (DPP)-based co-polymers. The co-polymers consisted of a DPP unit attached to a phenylene, naphthalene, or anthracene unit. Additionally, polymers utilizing either the thiophene-flanked DPP or the furan-flanked DPP units paired with the naphthalene comonomer were compared. As these polymers have been used as donor materials and subsequent hole transporting materials in organic solar cells, we are specifically interested in characterizing the optical absorption of the hole polaron of these DPP based copolymers. We employ chemical doping, electrochemical doping, and photoinduced absorption (PIA) studies to probe the hole polaron absorption spectra. While some donor-acceptor polymers have shown an appreciable capacity to generate free charge carriers upon photoexcitation, no polaron signal was observed in the PIA spectrum of the polymers in this study. The relations between molecular structure and optical properties are discussed. Polymers 2014-12-31 7 1 Article 10.3390/polym7010069 69 90 2073-4360 2014-12-31 doi: 10.3390/polym7010069 Evan Williams Ter Ang Zien Ooi Prashant Sonar Ting Lin Wei Neo Jing Song Jonathan Hobley http://www.mdpi.com/2073-4360/7/1/47 The present paper critically analyzes the potential for commercially available nanoparticles for enhancing the flame-retardant properties of synthetic and natural fabrics and their corresponding blends. Each nanoparticle has been applied to the fabric through a finishing-like process (namely impregnation/exhausting or, more simply, nanoparticle adsorption) in aqueous media and the resulting properties of these fabrics have been assessed in terms of combustion behavior by use of a cone calorimeter under a heat flux of 35 kW/m2. The influence of these nanoparticles on the main combustion parameters of polyester, cotton, and some of their blends has been thoroughly discussed. As a result of this discussion, a flame-retardant efficiency ranking of the nanoparticles under review has been established. Polymers 2014-12-31 7 1 Review 10.3390/polym7010047 47 68 2073-4360 2014-12-31 doi: 10.3390/polym7010047 Jenny Alongi Jennifer Tata Federico Carosio Giuseppe Rosace Alberto Frache Giovanni Camino http://www.mdpi.com/2073-4360/7/1/1 Individually, advances in microelectronics and biology transformed the way we live our lives. However, there remain few examples in which biology and electronics have been interfaced to create synergistic capabilities. We believe there are two major challenges to the integration of biological components into microelectronic systems: (i) assembly of the biological components at an electrode address, and (ii) communication between the assembled biological components and the underlying electrode. Chitosan possesses a unique combination of properties to meet these challenges and serve as an effective bio-device interface material. For assembly, chitosan's pH-responsive film-forming properties allow it to "recognize" electrode-imposed signals and respond by self-assembling as a stable hydrogel film through a cathodic electrodeposition mechanism. A separate anodic electrodeposition mechanism was recently reported and this also allows chitosan hydrogel films to be assembled at an electrode address. Protein-based biofunctionality can be conferred to electrodeposited films through a variety of physical, chemical and biological methods. For communication, we are investigating redox-active catechol-modified chitosan films as an interface to bridge redox-based communication between biology and an electrode. Despite significant progress over the last decade, many questions still remain which warrants even deeper study of chitosan's structure, properties, and functions. Polymers 2014-12-24 7 1 Review 10.3390/polym7010001 1 46 2073-4360 2014-12-24 doi: 10.3390/polym7010001 Eunkyoung Kim Yuan Xiong Yi Cheng Hsuan-Chen Wu Yi Liu Brian Morrow Hadar Ben-Yoav Reza Ghodssi Gary Rubloff Jana Shen William Bentley Xiaowen Shi Gregory Payne http://www.mdpi.com/2073-4360/6/12/3019 During thermoforming, plastic sheets are heated and subsequently deformed through the application of mechanical stretching and/or pressure. This process directly impacts sheet properties such as material thickness in walls, corners, and bottom, crystallinity in the constituent layers, and particularly the oxygen gas permeability. The aim of this study was to quantify the impact of thermoforming on thickness and oxygen transmission rate (OTR) of selected packaging materials (polypropylene (PP); PP/ethylene-vinyl alcohol co-polymer/PP (PP/EVOH/PP); polystyrene/EVOH/polyethylene (PS/EVOH/PE); amorphous polyethylene terephtalate/PE (APET/PE); APET/PE/EVOH/PE; polyamide/PE (PA/PE); and (PE/)PA/EVOH/PA/PE). These materials were extruded in two different thicknesses and thermoformed into trays with the same top dimensions and variable depths of 25, 50, and/or 75 mm and a 50 mm tray with a variable radius of the corners. The distribution of the material thickness in the trays was visualized, showing the locations that were most affected by the deep drawn process. The OTR results indicate that the calculated OTR, based on a homogeneous material distribution, can be used as a rough approximation of the measured OTR. However, detailed analysis of crystallization and unequal thinning, which is also related to the tray design, remains necessary to explain the deviation of the measured OTR as compared to the predicted one. Polymers 2014-12-22 6 12 Article 10.3390/polym6123019 3019 3043 2073-4360 2014-12-22 doi: 10.3390/polym6123019 Mieke Buntinx Gert Willems Griet Knockaert Dimitri Adons Jan Yperman Robert Carleer Roos Peeters http://www.mdpi.com/2073-4360/6/12/3005 There is growing evidence that the standard Weibull strength distribution is not always accurate for the description of variability in tensile strength and its dependence on the gauge size of brittle fibers. In this work, a modified Weibull model by incorporating the diameter variation of bamboo fiber is proposed to investigate the effect of fiber length and diameter on the tensile strength. Fiber strengths are obtained for lengths ranging from 20 to 60 mm and diameters ranging from 196.6 to 584.3 μm through tensile tests. It is shown that as the within-fiber diameter variation increases, the fracture strength of the bamboo fiber decreases. In addition, the accuracy of using weak-link scaling predictions based on the standard and modified Weibull distribution are assessed, which indicates that the use of the modified distribution provides better correlation with the experimental data than the standard model. The result highlights the accuracy of the modified Weibull model for characterizing the strength and predicting the size dependence of bamboo fiber. Polymers 2014-12-19 6 12 Article 10.3390/polym6123005 3005 3018 2073-4360 2014-12-19 doi: 10.3390/polym6123005 Fang Wang Jiaxing Shao http://www.mdpi.com/2073-4360/6/12/2985 Mixed phenolic-polyurethane-type rigid foams were developed using tannin-furfuryl alcohol natural materials co-reacted with polymeric isocyanate in the proportions imposed by the limitations inherent to continuous industrial plants for polyurethane foams. A variety of different copolymerization oligomers formed. Urethanes appeared to have been formed with two flavonoid tannin sites, mainly at the flavonoid hydroxyl group at C3, but also, although less, on the phenolic hydroxyl groups of the flavonoid oligomers. Urethanes are also formed with (i) glyoxal in the formulation, be it pre-reacted or not with the tannin; (ii) with phenolsulfonic acid and (iii) with furfural. This latter one, however, greatly favors reaction with the A-ring of the flavonoids through a methylene bridge rather than reaction with the isocyanate groups to form urethanes. All of the materials appeared to have co-reacted in a manner to form urethane and methylene bridges between all of the main components used. Thus, the tannin, the furfuryl alcohol, the isocyanate, the glyoxal and even the phenol sulfonic acid hardener formed a number of mixed species linked by the two bridge types. Several mixed species comprised of 2, 3 and even 4 co-reacted different components have been observed. Polymers 2014-12-17 6 12 Article 10.3390/polym6122985 2985 3004 2073-4360 2014-12-17 doi: 10.3390/polym6122985 Maria Basso Antonio Pizzi Clement Lacoste Luc Delmotte Fahad Al-Marzouki Soliman Abdalla Alain Celzard http://www.mdpi.com/2073-4360/6/12/2974 Skin loss is one of the oldest and still not totally resolved problems in the medical field. Since spontaneous healing of the dermal defects would not occur, the regeneration of full thickness of skin requires skin substitutes. Tissue engineering constructs would provide a three dimensional matrix for the reconstruction of skin tissue and the repair of damage. The aim of the present work is to develop a chitin based scaffold, by blending it with poly(butylene succinate) (PBS), an aliphatic, biodegradable and biocompatible synthetic polymer with excellent mechanical properties. The presence of chondroitin sulfate nanoparticles (CSnp) in the scaffold would favor cell adhesion. A chitin/PBS/CSnp composite hydrogel scaffold was developed and characterized by SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared Spectroscopy), and swelling ratio of scaffolds were analyzed. The scaffolds were evaluated for the suitability for skin tissue engineering application by cytotoxicity, cell attachment, and cell proliferation studies using human dermal fibroblasts (HDF). The cytotoxicity and cell proliferation studies using HDF confirm the suitability of the scaffold for skin regeneration. In short, these results show promising applicability of the developed chitin/PBS/CSnps ternary composite hydrogel scaffolds for skin tissue regeneration. Polymers 2014-12-16 6 12 Article 10.3390/polym6122974 2974 2984 2073-4360 2014-12-16 doi: 10.3390/polym6122974 S. Deepthi C. Viha Chaochai Thitirat Tetsuya Furuike Hiroshi Tamura Rangasamy Jayakumar http://www.mdpi.com/2073-4360/6/12/2961 The interfacial interactions of four methylcelluloses having the same average degree of substitution and distribution of methyl groups, but different molar masses, are studied at ambient temperature and at very low polymer concentrations. Firstly, the surface tension σ at the water/air interface is determined for the progressive addition of methylcellulose up to 100 mg/L; σ starts to decrease over 1 mg/L up to the critical aggregation concentration (CAC) at 10 mg/L. The curves describing the influence of polymer concentration on σ are independent of the molar mass at equilibrium. Secondly, the adsorption of methylcellulose on silica particles is estimated from ζ-potential measurements. The data are interpreted in terms of an increase of the adsorbed layer thickness at the interface when the molar mass of methylcellulose increases. It is concluded that methylcellulose is adsorbed, forming trains and loops at the interface based on the equilibrium between surface free energy and solvent quality. Polymers 2014-12-12 6 12 Article 10.3390/polym6122961 2961 2973 2073-4360 2014-12-12 doi: 10.3390/polym6122961 Pauline Nasatto Frédéric Pignon Joana Silveira Maria Duarte Miguel Noseda Marguerite Rinaudo http://www.mdpi.com/2073-4360/6/12/2942 By molecular dynamics simulations we investigate the transport of charged polymers in confinement, under externally applied electric fields, in straight cylinders of uniform diameter and in the presence of monovalent or multivalent counterions. The applied electric field has two components; a longitudinal component along the axis of the cylinder and a transversal component perpendicular to the cylinder axis. The direction of electrophoretic velocity depends on the polyelectrolyte length, valency of the counterions present in solution and transversal electric field value. A statistical model is put forward in order to explain these observations. Polymers 2014-12-04 6 12 Article 10.3390/polym6122942 2942 2960 2073-4360 2014-12-04 doi: 10.3390/polym6122942 Sorin Nedelcu Jens-Uwe Sommer http://www.mdpi.com/2073-4360/6/12/2928 Natural rubber (NR) is a high molecular weight natural polymer and can be degraded to liquid natural rubber (LNR) leaving certain functional groups at the end of chains. In this study, LNR samples prepared via oxidative degradation using H2O2 and NaNO2 as reagents were found to have different end groups depending on the pH of the reaction medium. In an acidic medium, LNR with hydroxyl terminal groups was formed as the degradation reaction was initiated by hydroxyl radicals produced from decomposition of peroxynitrite acid. In contrast, a redox reaction took place in an alkaline medium to yield LNR with carbonyl terminal groups. The mechanisms of reaction are discussed and proposed to explain the formation of different end groups when reaction carried out in acidic and alkaline media. Chain degradation in an acidic medium seems to be more effective than in an alkaline medium, and thus yields LNR with lower Mn. Polymers 2014-12-03 6 12 Article 10.3390/polym6122928 2928 2941 2073-4360 2014-12-03 doi: 10.3390/polym6122928 Suhawati Ibrahim Rusli Daik Ibrahim Abdullah http://www.mdpi.com/2073-4360/6/12/2912 Nanocomposites have attracted a great deal of interest during recent years. Much research has been conducted towards the incorporation of clay particles in a polypropylene matrix. However, the effect of extrusion reprocessing on the material properties has not been studied in depth. In this study, composites of polypropylene (PP) reinforced with organic modified montmorillonite (MMT) (4 wt%) and coupling agent were subjected to 15 extrusion cycles. The materials were characterized by melt flow index (MFI), plate-plate rheometry, tensile testing and impact measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed an improved intercalation of the MMT clay in the first few extrusions, thus improving the mechanical properties. Increasing the processing steps furthermore lead to a decrease in elastic modulus and impact strength, which was attributed to a reduction in matrix-filler interaction, most probably caused by organoclay degradation as shown by thermogravimetric analysis (TGA). The results of this study provide a useful insight in either the recycling of PP/MMT waste streams or the use of clay particles as a strengthening filler agent in the recycling process of different polymer waste streams. Polymers 2014-12-01 6 12 Article 10.3390/polym6122912 2912 2927 2073-4360 2014-12-01 doi: 10.3390/polym6122912 Laurens Delva Kim Ragaert Joris Degrieck Ludwig Cardon http://www.mdpi.com/2073-4360/6/12/2896 Silica in industrial production processes is precipitated by mixing an acid and an inorganic precursor. In this aqueous solution, silica particles form due to a polymerization reaction and agglomeration and, finally, build a gel. Thereafter, the reaction continues, and the gel network shrinks with the expulsion of the enclosed pore liquid. This slow process is known as "natural syneresis" and strongly affects the product properties, such as the agglomerate size, specific surface or porosity of the silica produced. In order to investigate the influence of process parameters, such as temperature, pH or ionic strength, on the shrinkage in shorter time-scales, we propose an acceleration of this process and define it as "enforced syneresis". The acceleration is performed by applying a mechanical external force to the gel by means of a plunger and measuring the shrinkage behavior under these conditions. Thereby, the conceptual idea is the prediction of the shrinkage due to natural syneresis based on the results of enforced syneresis. We are now able to predict the natural syneresis behavior from enforced syneresis data by the development of a correlative model. Using this prediction model, we can show the influence of temperature on the maximum shrinkage and on its rate in a significantly shorter time of about 12 h instead of several days. Polymers 2014-11-26 6 12 Article 10.3390/polym6122896 2896 2911 2073-4360 2014-11-26 doi: 10.3390/polym6122896 Sebastian Wilhelm Matthias Kind http://www.mdpi.com/2073-4360/6/11/2875 Thermally reduced graphite oxide (TRGO), containing only four single carbon layers on average, was combined with ammonium polyphosphate (APP) and magnesium hydroxide (MH), respectively, in polypropylene (PP). The nanoparticle's influence on different flame-retarding systems and possible synergisms in pyrolysis, reaction to small flame, fire behavior and mechanical properties were determined. TRGO has a positive effect on the yield stress, which is decreased by both flame-retardants and acts as a synergist with regard to Young's modulus. The applicability and effects of TRGO as an adjuvant in combination with conventional flame-retardants depends strongly on the particular flame-retardancy mechanism. In the intumescent system, even small concentrations of TRGO change the viscosity of the pyrolysing melt crucially. In case of oxygen index (OI) and UL 94 test, the addition of increasing amounts of TRGO to PP/APP had a negative impact on the oxygen index and the UL 94 classification. Nevertheless, systems with only low amounts (≤1 wt%) of TRGO achieved V-0 classification in the UL 94 test and high oxygen indices (>31 vol%). TRGO strengthens the residue structure of MH and therefore functions as a strong synergist in terms of OI and UL 94 classification (from HB to V-0). Polymers 2014-11-20 6 11 Article 10.3390/polym6112875 2875 2895 2073-4360 2014-11-20 doi: 10.3390/polym6112875 Bettina Dittrich Karen-Alessa Wartig Rolf Mülhaupt Bernhard Schartel http://www.mdpi.com/2073-4360/6/11/2862 Photochemically mediated reversible-deactivation radical polymerization of methyl methacrylate was successfully performed using 50–400 ppm of various copper compounds such as CuSO4·5H2O, copper acetate, copper triflate and copper acetylacetonate as catalysts. The copper catalysts were reduced in situ by irradiation at wavelengths of 366–546 nm, without using any additional reducing agent. Bromopropionitrile was used as an initiator. The effects of various solvents and the concentration and structure of ligands were investigated. Well-defined polymers were obtained when at least 100 or 200 ppm of any catalyst complexed with excess tris(2-pyridylmethyl)amine as a ligand was used in dimethyl sulfoxide as a solvent. Polymers 2014-11-14 6 11 Article 10.3390/polym6112862 2862 2874 2073-4360 2014-11-14 doi: 10.3390/polym6112862 Jaroslav Mosnáček Anna Kundys Anita Andicsová http://www.mdpi.com/2073-4360/6/11/2845 The generation of nano-microstructured surfaces is a current challenge in polymer science. The fabrication of such surfaces has been accomplished mainly following two different alternatives i.e., by adapting techniques, such as molding (embossing) or nano/microimprinting, or by developing novel techniques including laser ablation, soft lithography or laser scanning. Surface instabilities have been recently highlighted as a promising alternative to induce surface features. In particular, wrinkles have been extensively explored for this purpose. Herein, we describe the preparation of wrinkled interfaces by confining a photosensitive monomeric mixture composed of monofunctional monomer and a crosslinking agent within a substrate and a cover. The wrinkle characteristics can be controlled by the monomer mixture and the experimental conditions employed for the photopolymerization. More interestingly, incorporation within the material of a functional copolymer allowed us to vary the surface chemical composition while maintaining the surface structure. For that purpose we incorporated either a fluorinated copolymer that enhanced the surface hydrophobicity of the wrinkled interface or an acrylic acid containing copolymer that increased the hydrophilicity of the wrinkled surface. Finally, the role of the hydrophobicity on the bacterial surface adhesion will be tested by using Staphylococcus aureus. Polymers 2014-11-14 6 11 Article 10.3390/polym6112845 2845 2861 2073-4360 2014-11-14 doi: 10.3390/polym6112845 Marta Palacios-Cuesta Aitziber Cortajarena Olga García Juan Rodríguez-Hernández http://www.mdpi.com/2073-4360/6/11/2832 Water-based polymer nanoparticle dispersions (solar paint) offer the prospect of addressing two of the main challenges associated with printing large area organic photovoltaic devices; namely, how to control the nanoscale architecture of the active layer and eliminate the need for hazardous organic solvents during device fabrication. In this paper, we review progress in the field of nanoparticulate organic photovoltaic (NPOPV) devices and future prospects for large-scale manufacturing of solar cells based on this technology. Polymers 2014-11-13 6 11 Review 10.3390/polym6112832 2832 2844 2073-4360 2014-11-13 doi: 10.3390/polym6112832 Xiaojing Zhou Warwick Belcher Paul Dastoor http://www.mdpi.com/2073-4360/6/11/2819 Magnesium phosphate cement (MPC) has been proven to be a very good repair material for deteriorated concrete structures. It has excellent adhesion performance, leading to high bonding strength with old concrete substrates. This paper presents an experimental study into the properties of MPC binder as the matrix of carbon fiber sheets to form fiber-reinforced inorganic polymer (FRIP) composites. The physical and mechanical performance of the fresh mixed and the hardened MPC paste, the bond strength of carbon fiber sheets in the MPC matrix, the tensile strength of the carbon FRIP composites and the microstructure of the MPC matrix and fiber-reinforced MPC composites were investigated. The test results showed that the improved MPC binder is well suited for developing FRIP composites, which can be a promising alternative to externally-bonded fiber-reinforced polymer (FRP) composites for the strengthening of concrete structures. Through the present study, an in-depth understanding of the behavior of fiber-reinforced inorganic MPC composites has been achieved. Polymers 2014-11-12 6 11 Article 10.3390/polym6112819 2819 2831 2073-4360 2014-11-12 doi: 10.3390/polym6112819 Zhu Ding Jian-Guo Dai Sarfraz Muner http://www.mdpi.com/2073-4360/6/11/2803 Electrorheological (ER) and magnetorheological (MR) suspensions undergo a reverse phase transition from a liquid-like to solid-like state in response to an external electric or magnetic field, respectively. This paper briefly reviews various types of electro- or magneto-responsive materials from either polymeric or inorganic and hybrid composite materials. The fabrication strategies for ER/MR candidates and their ER/MR characteristics (particularly for ER fluids) are also included. Polymers 2014-11-05 6 11 Review 10.3390/polym6112803 2803 2818 2073-4360 2014-11-05 doi: 10.3390/polym6112803 Wen Zhang Hyoung Choi http://www.mdpi.com/2073-4360/6/11/2784 Bulk heterojunction (BHJ) organic photovoltaic (OPV) promise low cost solar energy and have caused an explosive increase in investigations during the last decade. Control over the 3D morphology of BHJ blend films in various length scales is one of the pillars accounting for the significant advance of OPV performance recently. In this contribution, we focus on the strategy of incorporating an additive into BHJ blend films as a morphological control agent, i.e., ternary blend system. This strategy has shown to be effective in tailoring the morphology of BHJ through different inter- and intra-molecular interactions. We systematically review the morphological observations and associated mechanisms with respect to various kinds of additives, i.e., polymers, small molecules and inorganic nanoparticles. We organize the effects of morphological control (compatibilization, stabilization, etc.) and provide general guidelines for rational molecular design for additives toward high efficiency and high stability organic solar cells. Polymers 2014-11-03 6 11 Review 10.3390/polym6112784 2784 2802 2073-4360 2014-11-03 doi: 10.3390/polym6112784 Hsueh-Chung Liao Po-Hsuen Chen Robert Chang Wei-Fang Su http://www.mdpi.com/2073-4360/6/11/2764 This study investigates chemical grafting with fatty acid chlorides as a method for the surface modification of hydrophilic web materials. The resulting changes in the water repellence and barrier properties were studied. For this purpose, different grades of polyvinyl alcohol (PVOH) were coated on regenerated cellulose films ("cellophane") and paper and then grafted with fatty acid chlorides. The PVOH grades varied in their degree of hydrolysis and average molecular weight. The surface was esterified with two fatty acid chlorides, palmitoyl (C16) and stearoyl chloride (C18), by chemical grafting. The chemical grafting resulted in water-repellent surfaces and reduced water vapor transmission rates by a factor of almost 19. The impact of the surface modification was greater for a higher degree of hydrolysis of the polyvinyl alcohol and for shorter fatty acid chains. Although the water vapor barrier for palmitoyl-grafted PVOH was higher than for stearoyl-grafted PVOH, the contact angle with water was lower. Additionally, it was shown that a higher degree of hydrolysis led to higher water vapor barrier improvement factors after grafting. Furthermore, the oxygen permeability decreased after grafting significantly, due to the fact that the grafting protects the PVOH against humidity when the humidity is applied on the grafted side. It can be concluded that the carbon chain length of the fatty acid chlorides is the limiting factor for water vapor adsorption, but the grafting density is the bottleneck for water diffusing in the polymer. Polymers 2014-11-03 6 11 Article 10.3390/polym6112764 2764 2783 2073-4360 2014-11-03 doi: 10.3390/polym6112764 Markus Schmid Sven Sängerlaub Oliver Miesbauer Verena Jost Johannes Werthan Camelia Stinga Daniel Samain Cornelia Stramm Klaus Noller Kajetan Müller http://www.mdpi.com/2073-4360/6/11/2752 The miscibility and phase behavior of poly(4-vinylphenol) (PVPh) with poly(vinyl methyl ketone) (PVMK) was investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was shown that all blends of PVPh/PVMK are totally miscible. A DSC study showed the apparition of a single glass transition (Tg) over their entire composition range. When the amount of PVPh exceeds 50% in blends, the obtained Tgs are found to be significantly higher than those observed for each individual component of the mixture, indicating that these blends are capable of forming interpolymer complexes. FTIR analysis revealed the existence of preferential specific interactions via hydrogen bonding between the hydroxyl and carbonyl groups, which intensified when the amount of PVPh was increased in blends. Furthermore, the quantitative FTIR study carried out for PVPh/PVMK blends was also performed for the vinylphenol (VPh) and vinyl methyl ketone (VMK) functional groups. These results were also established by scanning electron microscopy study (SEM). Polymers 2014-10-28 6 11 Article 10.3390/polym6112752 2752 2763 2073-4360 2014-10-28 doi: 10.3390/polym6112752 Hana Bourara Slimane Hadjout Zitouni Benabdelghani Agustin Etxeberria http://www.mdpi.com/2073-4360/6/11/2737 Coupling reactions were performed to gauge the effect of the inclusion of a radical trap on the success of coupling reactions of monohalogenated polystyrene (PSX) chains in atom transfer radical coupling (ATRC) type reactions. The effect of both the specific radical trap chosen and the structure of the polymer chain end were evaluated by the extent of dimerization observed in a series of analogous coupling reactions. The commonly used radical trap 2-methyl-2-nitrosopropane (MNP) showed the highest amounts of dimerization for PSX (X = Br, Cl) compared to coupling reactions performed in its absence or with a different radical trap. A dinitroxide coupling agent was also studied with the extent of coupling nearly matching the effectiveness of MNP in RTA (Radical trap-assisted)-ATRC reactions, while N-nitroso and electron rich nitroso coupling agents were the least effective. (2,2,6,6-Tetramethyl-piperin-l-yl)oxyl-capped PS (PS-TEMPO), prepared by NMP, was subjected to a coupling sequence conceptually similar to RTA-ATRC, but dimerization was not observed regardless of the choice of radical trap. Kinetic experiments were performed to observe rate changes on the coupling reaction of PSBr as a result of the inclusion of MNP, with substantial rate enhancements found in the RTA-ATRC coupling sequence compared to traditional ATRC. Polymers 2014-10-24 6 11 Article 10.3390/polym6112737 2737 2751 2073-4360 2014-10-24 doi: 10.3390/polym6112737 Elizabeth Carnicom Jessica Abruzzese Yacouba Sidibe Kenneth Myers Eric Tillman http://www.mdpi.com/2073-4360/6/11/2720 Proton exchange membranes (PEMs) are a key component of a proton exchange membrane fuel cell. Sulfonated polyimides (SPIs) were doped by protic ionic liquid (PIL) to prepare composite PEMs with substantially improved conductivity. SPIs were synthesized from diamine, 2,2-bis[4-(4-amino-phenoxy)phenyl]propane (BAPP), sulfonated diamine, 4,4'-diamino diphenyl ether-2,2'-disulfonic acid (ODADS) and aromatic anhydride. BAPP improved the mechanical and thermal properties of SPIs, while ODADS enhanced conductivity. A PIL, 1-vinylimidazolium trifluoromethane-sulfonate ([VIm][OTf]), was utilized. [VIm][OTf] offered better conductivity, which can be attributed to its vinyl chemical structure attached to an imidazolium ring that contributed to ionomer-PIL interactions. We prepared sulfonated polyimide/ionic liquid (SPI/IL) composite PEMs using 50 wt% [VIm][OTf] with a conductivity of 7.17 mS/cm at 100 °C, and in an anhydrous condition, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA) was used in the synthesis of SPIs, leading to several hundred-times improvement in conductivity compared to pristine SPIs. Polymers 2014-10-24 6 11 Article 10.3390/polym6112720 2720 2736 2073-4360 2014-10-24 doi: 10.3390/polym6112720 Bor-Kuan Chen Jhong-Ming Wong Tzi-Yi Wu Lung-Chuan Chen I-Chao Shih http://www.mdpi.com/2073-4360/6/10/2684 Proteins are heteropolymers that play important roles in virtually every biological reaction. While many proteins have well-defined three-dimensional structures that are inextricably coupled to their function, intrinsically disordered proteins (IDPs) do not have a well-defined structure, and it is this lack of structure that facilitates their function. As many IDPs are involved in essential cellular processes, various diseases have been linked to their malfunction, thereby making them important drug targets. In this review we discuss methods for studying IDPs and provide examples of how computational methods can improve our understanding of IDPs. We focus on two intensely studied IDPs that have been implicated in very different pathologic pathways. The first, p53, has been linked to over 50% of human cancers, and the second, Amyloid-β (Aβ), forms neurotoxic aggregates in the brains of patients with Alzheimer's disease. We use these representative proteins to illustrate some of the challenges associated with studying IDPs and demonstrate how computational tools can be fruitfully applied to arrive at a more comprehensive understanding of these fascinating heteropolymers. Polymers 2014-10-23 6 10 Review 10.3390/polym6102684 2684 2719 2073-4360 2014-10-23 doi: 10.3390/polym6102684 Virginia Burger Thomas Gurry Collin Stultz http://www.mdpi.com/2073-4360/6/10/2670 Thermo-responsive diblock copolymers composed of hydrophilic methoxy poly(ethylene glycol) (MPEG) and hydrophobic biodegradable polyesters were prepared for application as injectable drug delivery systems, because they show a thermo-responsive sol-to-gel transition, especially around body temperature, when dispersed in aqueous solutions. The thermogelling hydrogels formed by hydrophobic aggregation could be varied by changing the components of the hydrophobic polyester part. For the polyester block in the present study, 95 mol% of ε-caprolactone (CL) was used for the main polyester chain and 5 mol% of p-dioxanone (DO) was copolymerized randomly by the MPEG initiator in the presence of HCl as the catalyst. By adding a small portion of DO into the poly ε-caprolactone (PCL) chains, the temperature range of gelation, the intensity of viscosity and the drug release behavior were changed. The MPEG-b-poly(ε-caprolactone-ran-p-dioxanone) (MPEG-b-PCDO) hydrogel showed the enhanced drug release in vitro and in vivo compared to MPEG-b-PCL hydrogel. Therefore, MPEG-polyester hydrogels may serve as minimally invasive and therapeutic, injectable hydrogel systems with adjustable temperature-responsive and biodegradable windows, as well as sustained release of drugs over a certain time period. Polymers 2014-10-23 6 10 Article 10.3390/polym6102670 2670 2683 2073-4360 2014-10-23 doi: 10.3390/polym6102670 Hoon Hyun Seung Park Doo Kwon Gilson Khang Hai Lee Moon Kim http://www.mdpi.com/2073-4360/6/10/2645 Organic photovoltaics (OPVs) and dye-sensitized solar cells (DSSCs) have drawn great interest from both academics and industry, due to the possibility of low-cost conversion of photovoltaic energy at reasonable efficiencies. This review focuses on recent progress in molecular engineering and technological aspects of fused-thiophene-based organic dye molecules for applications in solar cells. Particular attention has been paid to the design principles and stability of these dye molecules, as well as on the effects of various electrolyte systems for DSSCs. Importantly, it has been found that incorporation of a fused-thiophene unit into the sensitizer has several advantages, such as red-shift of the intramolecular charge transfer band, tuning of the frontier molecular energy level, and improvements in both photovoltaic performance and stability. This work also examines the correlation between the physical properties and placement of fused-thiophene in the molecular structure with regard to their performance in OPVs and DSSCs. Polymers 2014-10-22 6 10 Review 10.3390/polym6102645 2645 2669 2073-4360 2014-10-22 doi: 10.3390/polym6102645 Prabakaran Kumaresan Sureshraju Vegiraju Yamuna Ezhumalai Shueh Yau Choongik Kim Wen-Hsi Lee Ming-Chou Chen http://www.mdpi.com/2073-4360/6/10/2625 The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA) has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC) were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity decrease caused by oxidative system, indicating HA protection from degradation, SEC analysis suggested that some other mechanisms leading to the bucillamine transformations without the decay of the viscosity may come into a play as well. Nonetheless, the link between the reduction of chemiluminescence intensity and disappearance of the differential scanning calorimetry exotherm at 270 °C for fragmented HAs indicates a particular role of the bucillamine in preventing the decrease of HA viscosity. Polymers 2014-10-21 6 10 Article 10.3390/polym6102625 2625 2644 2073-4360 2014-10-21 doi: 10.3390/polym6102625 Mária Baňasová Katarína Valachová Jozef Rychlý Ivica Janigová Katarína Csomorová Raniero Mendichi Danica Mislovičová Ivo Juránek Ladislav Šoltés http://www.mdpi.com/2073-4360/6/10/2611 The aim of the present study was to determine the influence of sulphuric acid hydrolysis and high-pressure homogenization as an effective chemo-mechanical process for the isolation of quality nanofibrillated cellulose (NFC). The cellulosic fiber was isolated from oil palm empty fruit bunch (OPEFB) using acid hydrolysis methods and, subsequently, homogenized using a high-pressure homogenizer to produce NFC. The structural analysis and the crystallinity of the raw fiber and extracted cellulose were carried out by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The morphology and thermal stability were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric (TGA) analyses, respectively. The FTIR results showed that lignin and hemicellulose were removed effectively from the extracted cellulose nanofibrils. XRD analysis revealed that the percentage of crystallinity was increased from raw EFB to microfibrillated cellulose (MFC), but the decrease for NFC might due to a break down the hydrogen bond. The size of the NFC was determined within the 5 to 10 nm. The TGA analysis showed that the isolated NFC had high thermal stability. The finding of present study reveals that combination of sulphuric acid hydrolysis and high-pressure homogenization could be an effective chemo-mechanical process to isolate cellulose nanofibers from cellulosic plant fiber for reinforced composite materials. Polymers 2014-10-21 6 10 Article 10.3390/polym6102611 2611 2624 2073-4360 2014-10-21 doi: 10.3390/polym6102611 Ireana Fatah H. Khalil Md. Hossain Astimar Aziz Yalda Davoudpour Rudi Dungani Amir Bhat http://www.mdpi.com/2073-4360/6/10/2588 In this paper, we propose to review the ways to produce, through photopolymerization, interpenetrating polymer networks (IPN) based, e.g., on acrylate/epoxide or acrylate/vinylether blends and to outline the recent developments that allows a one-step procedure (concomitant radical/cationic polymerization), under air or in laminate, under various irradiation conditions (UV/visible/near IR; high/low intensity sources; monochromatic/polychromatic sources; household lamps/laser diodes/Light Emitting Diodes (LEDs)). The paper illustrates the encountered mechanisms and the polymerization profiles. A short survey on the available monomer systems and some brief examples of the attained final properties of the IPNs is also provided. Polymers 2014-10-20 6 10 Review 10.3390/polym6102588 2588 2610 2073-4360 2014-10-20 doi: 10.3390/polym6102588 Jean Fouassier Jacques Lalevée http://www.mdpi.com/2073-4360/6/10/2573 Mannose polyethylenimine with a molecular weight of 25 k (Man-PEI25k) was synthesized via a phenylisothiocyanate bridge using mannopyranosylphenyl isothiocyanate as a coupling reagent, and characterized by 1H NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infrared spectroscopy) analysis. Spherical nanoparticles were formed with diameters of 80–250 nm when the copolymer was mixed with DNA at various charge ratios of copolymer/DNA (N/P). Gel electrophoresis demonstrated that the DNA had been condensed and retained by the PEI derivates at low N/P ratios. The Man-PEI25k/DNA complexes were less cytotoxic than the PEI complexes with a molecular weight of 25 k (PEI25k) at the same N/P ratio. Laser scan confocal microscopy and flow cytometry confirmed that the Man-PEI25k/DNA complexes gave higher cell uptake efficiency in (Dendritic cells) DC2.4 cells than HeLa cells. The transfection efficiency of Man-PEI25k was higher than that of PEI25k towards DC2.4 cells. These results indicated that Man-PEI25k could be used as a potential DC-targeting non-viral vector for gene therapy. Polymers 2014-10-17 6 10 Article 10.3390/polym6102573 2573 2587 2073-4360 2014-10-17 doi: 10.3390/polym6102573 Ying Hu Bei-Hua Xu Jiao-Jiao Xu Dan Shou Jian-Qing Gao http://www.mdpi.com/2073-4360/6/10/2552 In this paper, we propose a simple one-pot methodology for proceeding from atom transfer reaction-induced conventional free radical polymerization (AT-FRP) to atom transfer self-condensing vinyl polymerization (AT-SCVP) through manipulation of the catalyst phase homogeneity (i.e., CuBr/2,2'-bipyridine (CuBr/Bpy)) in a mixture of styrene (St), 4-vinyl benzyl chloride (VBC), and ethyl 2-bromoisobutyrate. Tests of the solubilities of CuBr/Bpy and CuBr2/Bpy under various conditions revealed that both temperature and solvent polarity were factors affecting the solubility of these copper complexes. Accordingly, we obtained different polymer topologies when performing AT-SCVP in different single solvents. We investigated two different strategies to control the polymer topology in one-pot: varying temperature and varying solvent polarity. In both cases, different fractions of branching revealed the efficacy of varying the polymer topology. To diversify the functionality of the peripheral space, we performed chain extensions of the resulting hyperbranched poly(St-co-VBC) macroinitiator (name as: hbPSt MI) with either St or tBA (tert-butyl acrylate). The resulting hyperbranched core star polymer had high molecular weights (hbPSt-g-PSt: Mn = 25,000, Đ = 1.77; hbPSt-g-PtBA: Mn = 27,000, Đ = 1.98); hydrolysis of the tert-butyl groups of the later provided a hyperbranched core star polymer featuring hydrophilic poly(acrylic acid) segments. Polymers 2014-09-30 6 10 Article 10.3390/polym6102552 2552 2572 2073-4360 2014-09-30 doi: 10.3390/polym6102552 Zong-Cheng Chen Chia-Ling Chiu Chih-Feng Huang http://www.mdpi.com/2073-4360/6/10/2526 Tissue contacting surfaces of medical devices initiate a host inflammatory response, characterized by adsorption of blood proteins and inflammatory cells triggering the release of cytokines, reactive oxygen species (ROS) and reactive nitrogen species (RNS), in an attempt to clear or isolate the foreign object from the body. This normal host response contributes to device-associated pathophysiology and addressing device biocompatibility remains an unmet need. Although widespread attempts have been made to render the device surfaces unreactive, the establishment of a completely bioinert coating has been untenable and demonstrates the need to develop strategies based upon the molecular mechanisms that define the interaction between host cells and synthetic surfaces. In this review, we discuss a family of transmembrane receptors, known as immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing receptors, which show promise as potential targets to address aberrant biocompatibility. These receptors repress the immune response and ensure that the intensity of an immune response is appropriate for the stimuli. Particular emphasis will be placed on the known ITIM-containing receptor, Signal Regulatory Protein Alpha (SIRPα), and its cognate ligand CD47. In addition, this review will discuss the potential of other ITIM-containing proteins as targets for addressing the aberrant biocompatibility of polymeric biomaterials. Polymers 2014-09-29 6 10 Review 10.3390/polym6102526 2526 2551 2073-4360 2014-09-29 doi: 10.3390/polym6102526 Joshua Slee Abigail Christian Robert Levy Stanley Stachelek http://www.mdpi.com/2073-4360/6/10/2510 The aim of this work is to evaluate the potential of cryogels to be used as scaffolds in tissue engineering. Scaffolds based on the α-tricalcium phosphate reinforced PDMAEMA (Poly(dimethyl aminoethyl methacrylate))/PHEMA (poly(hydroxyethyl methacrylate)) system were prepared and human trabecular bone-derived cells (HTBs) and bone marrow derived-mesenchymal stem cells (BM-MSCs) cultured on them. Several features, such as porosity, pore shape, molecular weight between crosslinks and mesh size, are studied. The most suitable PDMAEMA/PHEMA ratio for cell proliferation has been assessed and the viability, adhesion, proliferation and expression of osteoblastic biochemical markers are evaluated. The PDMAEMA/PHEMA ratio influences the scaffolds porosity. Values between 53% ± 5.7% for a greater content in PHEMA and 75% ± 5.5% for a greater content in PDMAEMA have been obtained. The polymer ratio also modifies the pore shape. A greater content in PDMAEMA leads also to bigger network mesh size. Each of the compositions were non-cytotoxic, the seeded cells remained viable for both BM-MSCs and HTBs. Thus, and based on the structural analysis, specimens with a greater content in PDMAEMA seem to provide a better structural environment for their use as scaffolds for tissue engineering. The α-tricalcium phosphate incorporation into the composition seems to favor the expression of the osteogenic phenotype. Polymers 2014-09-29 6 10 Article 10.3390/polym6102510 2510 2525 2073-4360 2014-09-29 doi: 10.3390/polym6102510 Tiago Volkmer Joana Magalhães Vania Sousa Luis Santos Elena Burguera Francisco Blanco Julio Román Luis Rodríguez-Lorenzo http://www.mdpi.com/2073-4360/6/9/2473 Organic photovoltaic cells (OPVs) have been a hot topic for research during the last decade due to their promising application in relieving energy pressure and environmental problems caused by the increasing combustion of fossil fuels. Much effort has been made toward understanding the photovoltaic mechanism, including evolving chemical structural motifs and designing device structures, leading to a remarkable enhancement of the power conversion efficiency of OPVs from 3% to over 15%. In this brief review, the advanced progress and the state-of-the-art performance of OPVs in very recent years are summarized. Based on several of the latest developed approaches to accurately detect the separation of electron-hole pairs in the femtosecond regime, the theoretical interpretation to exploit the comprehensive mechanistic picture of energy harvesting and charge carrier generation are discussed, especially for OPVs with bulk and multiple heterojunctions. Subsequently, the novel structural designs of the device architecture of OPVs embracing external geometry modification and intrinsic structure decoration are presented. Additionally, some approaches to further increase the efficiency of OPVs are described, including thermotics and dynamics modification methods. Finally, this review highlights the challenges and prospects with the aim of providing a better understanding towards highly efficient OPVs. Polymers 2014-09-25 6 9 Review 10.3390/polym6092473 2473 2509 2073-4360 2014-09-25 doi: 10.3390/polym6092473 Junsheng Yu Yifan Zheng Jiang Huang http://www.mdpi.com/2073-4360/6/9/2451 The release of monovalent potassium and divalent calcium ions from zwitterionic phosphorylcholine containing poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogels was studied and the effects of polymer swelling, ion valence and temperature were investigated. For comparison, ions were loaded during hydrogel formulation or loaded by partitioning following construct synthesis. Using the Koshmeyer-Peppas release model, the apparent diffusion coefficient, Dapp, and diffusional exponents, n, were Dapp (pre-K+) = 2.03 × 10−5, n = 0.4 and Dapp (post-K+) = 1.86 × 10−5, n = 0.33 respectively, indicative of Fickian transport. The Dapp (pre-Ca2+) = 3.90 × 10−6, n = 0.60 and Dapp (post-Ca2+) = 2.85 × 10−6, n = 0.85, respectively, indicative of case II and anomalous transport. Results indicate that divalent cations form cation-polyelectrolyte anion polymer complexes while monovalent ions do not. Temperature dependence of potassium ion release was shown to follow an Arrhenius-type relation with negative apparent activation energy of −19 ± 15 while calcium ion release was temperature independent over the physiologically relevant range (25–45 °C) studied. The negative apparent activation energy may be due to temperature dependent polymer swelling. No effect of polymer swelling on the diffusional exponent or rate constant was found suggesting polymer relaxation occurs independent of polymer swelling. Polymers 2014-09-25 6 9 Article 10.3390/polym6092451 2451 2472 2073-4360 2014-09-25 doi: 10.3390/polym6092451 A. Wilson Mark Blenner Anthony Guiseppi-Elie http://www.mdpi.com/2073-4360/6/9/2435 This article reports a simultaneous synthesis of polyaniline (PANI) and nickel (Ni) nanoparticles embedded in polyvinyl alcohol (PVA) film matrix by gamma radiolytic method. The mechanism of formation of PANI and Ni nanoparticles were proposed via oxidation of aniline and reduction of Ni ions, respectively. The effects of dose and Ni ions concentration on structural, optical, and electrical properties of the final PVA/PANI/Ni nanocomposites film were carefully examined. The structural and morphological studies show the presence of PANI with irregular granular microstructure and Ni nanoparticles with spherical shape and diameter less than 60 nm. The average particle size of Ni nanoparticles decreased with increasing dose and decreasing of precursor concentration due to increase of nucleation process over aggregation process during gamma irradiation. The optical absorption spectra showed that the absorption peak of Ni nanoparticles at about 390 nm shifted to lower wavelength and the absorbance increased with increasing dose. The formation of PANI was also revealed at 730 nm absorption peak with the absorbance increasing by the increase of dose. The electrical conductivity increased with increasing of dose and chlorine concentration due to number of polarons formation increases in the PVA/PANI/Ni nanocomposites. Polymers 2014-09-24 6 9 Article 10.3390/polym6092435 2435 2450 2073-4360 2014-09-24 doi: 10.3390/polym6092435 Abdo Meftah Elham Gharibshahi Nayereh Soltani W. Yunus Elias Saion http://www.mdpi.com/2073-4360/6/9/2433 The authors wish to make the following corrections to this paper [1]. [...] Polymers 2014-09-22 6 9 Correction 10.3390/polym6092433 2433 2434 2073-4360 2014-09-22 doi: 10.3390/polym6092433 Qingchuan Guo Reza Ghadiri Thomas Weigel Andreas Aumann Evgeny Gurevich Cemal Esen Olaf Medenbach Wei Cheng Boris Chichkov Andreas Ostendorf http://www.mdpi.com/2073-4360/6/9/2404 Recent progress of simulations/modeling at the atomic level has led to a better understanding of the mechanical behaviors of graphene, which include the linear elastic modulus E, the nonlinear elastic modulus D, the Poisson's ratio ν, the intrinsic strength σint and the corresponding strain εint as well as the ultimate strain εmax (the fracture strain beyond which the graphene lattice will be unstable). Due to the two-dimensional geometric characteristic, the in-plane tensile response and the free-standing indentation response of graphene are the focal points in this review. The studies are based on multiscale levels: including quantum mechanical and classical molecular dynamics simulations, and parallel continuum models. The numerical studies offer useful links between scientific research with engineering application, which may help to fulfill graphene potential applications such as nano sensors, nanotransistors, and other nanodevices. Polymers 2014-09-22 6 9 Review 10.3390/polym6092404 2404 2432 2073-4360 2014-09-22 doi: 10.3390/polym6092404 Guoxin Cao http://www.mdpi.com/2073-4360/6/9/2386 Polylactic acid (PLA) and montmorillonite (CB) as filler were studied as coatings for cellulose based packages. Amorphous (AM) and semi crystalline (SC) PLA were used at different concentrations according to a 2 × 6 × 3 full factorial experimental design. CB loading was three concentrations and coating was performed by casting. Contact angle (CA), water vapor (WVP) and grease permeabilities were measured for each resultant package and were compared to commercial materials (Glassine Paper, Grease Proof Papers 1 and 2 produced commercially). Significant differences were found and the main factors were the type and concentration of PLA. The best values were: for grease penetration, +1800 s; WVP from 161.36 to 237.8 g·µm·kPa−1·m−2·d−1 and CA from 69° to 73° for PLA–AM 0.5% and CB variable. These parameters are comparable to commercial packages used in the food industry. DSC revealed three different thermal events for PLA–SC and just Tg for PLA–AM. Crystallinity was also verified, obtaining a ΔHcrys of 3.7 J·g−1 for PLA–SC and 14 J·g−1 for PLA–SC–BC, evidencing clay interaction as a crystal nucleating agent. Differences found were explained on terms of the properties measured, where structural and chemical arrays of the coatings play a fundamental role for the barrier properties. Polymers 2014-09-19 6 9 Article 10.3390/polym6092386 2386 2403 2073-4360 2014-09-19 doi: 10.3390/polym6092386 Daniela Aldana Eduardo Villa Miguel De Dios Hernández Guillermo Sánchez Quintín Cruz Sergio Gallardo Hilda Castillo Lourdes Casarrubias http://www.mdpi.com/2073-4360/6/9/2371 A cellulose derivative, carboxymethyl cellulose (CMC), was synthesized by the reaction of cellulose from kenaf bast fiber with monochloroacetic acid. A series of biopolymer electrolytes comprised of the synthesized CMC and ammonium acetate (CH3COONH4) were prepared by the solution-casting technique. The biopolymer-based electrolyte films were characterized by Fourier Transform Infrared spectroscopy to investigate the formation of the CMC–CH3COONH4 complexes. Electrochemical impedance spectroscopy was conducted to obtain their ionic conductivities. The highest conductivity at ambient temperature of 5.77 × 10−4 S cm−1 was obtained for the electrolyte film containing 20 wt% of CH3COONH4. The biopolymer electrolyte film also exhibited electrochemical stability up to 2.5 V. These results indicated that the biopolymer electrolyte has great potential for applications to electrochemical devices, such as proton batteries and solar cells. Polymers 2014-09-19 6 9 Article 10.3390/polym6092371 2371 2385 2073-4360 2014-09-19 doi: 10.3390/polym6092371 Mohd Rani Siti Rudhziah Azizan Ahmad Nor Mohamed http://www.mdpi.com/2073-4360/6/9/2357 In this work, amidoxime polyacrylonitrile (AOPAN) nanofibrous membrane was prepared by a reaction between PAN nanofibers and hydroxylamine hydrochloride. The AOPAN nanofibrous membranes were used for four metal ions (Fe3+, Cu2+, Ni2+, Cd2+) chelation under different conditions. Further, the competition of different metal ions coordinating with AOPAN nanofibrous membrane was also studied. The AOPAN chelated with individual metal ion (Fe3+, Cu2+, Ni2+, Cd2+) and also the four mixed metal ions were further used for laccase (Lac) immobilization. Compared with free laccase, the immobilized laccase showed better resistance to pH and temperature changes as well as improved storage stability. Among the four individual metal ion chelated membranes, the stability of the immobilized enzymes generally followed the order as Fe–AOPAN–Lac > Cu–AOPAN–Lac > Ni–AOPAN–Lac > Cd–AOPAN–Lac. In addition, the immobilized enzyme on the carrier of AOPAN chelated with four mixed metal ions showed the best properties. Polymers 2014-09-15 6 9 Article 10.3390/polym6092357 2357 2370 2073-4360 2014-09-15 doi: 10.3390/polym6092357 Qingqing Wang Jing Cui Guohui Li Jinning Zhang Fenglin Huang Qufu Wei http://www.mdpi.com/2073-4360/6/9/2345 Cellulose woven (CW) was surface treated by means of hexadecyltrimethylammonium bromide surfactant (HTAB) in aqueous solution medium at elevated temperature. The parameters of the surface treatment that have been studied are HTAB concentration (0.2, 0.4, 0.6, 0.8 and 1.0 wt%) and treatment time (1, 2, 3, 4 and 5 h). The untreated and treated CW filled low-density polyethylene (LDPE) biocomposites were prepared via compression molding technique. The tensile testing results of LDPE/CW biocomposites demonstrated that the optimum HTAB concentration for treatment of CW in 1 h was 0.4 wt%, while the optimum treatment time at 0.4 wt% HTAB was 2 h. The SEM (scanning electron microscope) images indicated that there is no significant difference in the morphology of the untreated and treated CW; however the morphology of the LDPE/treated CW biocomposite showed better interfacial adhesion as compared with the untreated ones. The FTIR (Fourier transform infrared spectroscopy) spectra revealed that the presence of HTAB on the surface of treated CW and also revealed the existence of intermolecular interactions between LDPE and treated CW. In summary, HTAB could potentially be used as a treatment agent for modifying the surface of CW and consequently improved the tensile properties of LDPE/CW biocomposites. Polymers 2014-09-12 6 9 Communication 10.3390/polym6092345 2345 2356 2073-4360 2014-09-12 doi: 10.3390/polym6092345 Ahmad Shamsuri Muhammad Azid Azmah Ariff Ahmad Sudari http://www.mdpi.com/2073-4360/6/9/2332 The synthesis and characterization of ZnS/PMMA (poly(methyl methacrylate)), CdS/PMMA and HgS/PMMA nanocomposites are presented. Hexadecylamine (HDA)-capped ZnS, CdS and HgS nanoparticles were synthesized using dithiocarbamate single molecule precursors at 180 °C. FTIR (Fourier transform infrared spectroscopy) spectra measurement confirmed the dispersion of the metal sulfide nanoparticles in the PMMA matrices to form the metal sulfides/PMMA nanocomposites. Powder X-ray diffraction confirmed the presence of the amorphous PMMA in the nanocomposites. The ZnS and HgS particles were indexed to the cubic phase, while the HgS particles correspond to the hexagonal phase. Thermogravimetric analyses showed that the metal sulfide nanocomposites are thermally more stable than their corresponding precursor complexes. The TEM (Transmission electron microscope) analyses revealed that the ZnS nanoparticles have a particle size of 3–5 nm; the crystallite size of the CdS nanoparticles is 6–12 nm, and HgS nanoparticles are 6–12 nm. Polymers 2014-09-05 6 9 Article 10.3390/polym6092332 2332 2344 2073-4360 2014-09-05 doi: 10.3390/polym6092332 Johannes Mbese Peter Ajibade http://www.mdpi.com/2073-4360/6/9/2309 The search for a single material with ideal surface properties and necessary mechanical properties is on-going, especially with regard to cardiovascular stent materials. Since the majority of stent problems arise from surface issues rather than bulk material deficiencies, surface optimization of a material that already contains the necessary bulk properties is an active area of research. Polymers can be surface-modified using a variety of methods to increase hemocompatibilty by reducing either late-stage restenosis or acute thrombogenicity, or both. These modification methods can be extended to shape memory polymers (SMPs), in an effort to make these materials more surface compatible, based on the application. This review focuses on the role of surface modification of materials, mainly polymers, to improve the hemocompatibility of stent materials; additional discussion of other materials commonly used in stents is also provided. Although shape memory polymers are not yet extensively used for stents, they offer numerous benefits that may make them good candidates for next-generation stents. Surface modification techniques discussed here include roughening, patterning, chemical modification, and surface modification for biomolecule and drug delivery. Polymers 2014-08-29 6 9 Review 10.3390/polym6092309 2309 2331 2073-4360 2014-08-29 doi: 10.3390/polym6092309 Tina Govindarajan Robin Shandas http://www.mdpi.com/2073-4360/6/8/2287 This paper provides a brief review on the advanced shape memory technology (ASMT) with a focus on polymeric materials. In addition to introducing the concept and fundamentals of the ASMT, the potential applications of the ASMT either alone or integrated with an existing mature technique (such as, 3D printing, quick response (QR) code, lenticular lens) and phenomena (e.g., wrinkling and stress-enhanced swelling effect) in product design, manufacturing, and recycling are demonstrated. It is concluded that the ASMT is indeed able to provide a range of powerful approaches to reshape part of the life cycle or the whole life cycle of products. Polymers 2014-08-22 6 8 Review 10.3390/polym6082287 2287 2308 2073-4360 2014-08-22 doi: 10.3390/polym6082287 Wen Yang Haibao Lu Wei Huang Hang Qi Xue Wu Ke Sun http://www.mdpi.com/2073-4360/6/8/2274 A conductive epoxy-based shape memory polymer (SMP) is demonstrated using carbon black (CB) as a dopant for the purpose of creating an SMP dry adhesive system which can internally generate the heat required for activation. The electrical and mechanical properties of the CB/SMP blends for varying dopant concentrations are characterized. A composite adhesive is created to minimize surface contact resistance to conductive tape acting as electrodes, while maintaining bulk resistivity required for heat generation due to current flow. The final adhesive can function on flat or curved surfaces. As a demonstration, a 25 mm wide by 45 mm long dry adhesive strip is shown to heat evenly from an applied voltage, and can easily hold a mass in excess of 6 kg when bonded to a spherical concave glass surface using light pressure at 75 °C. Polymers 2014-08-22 6 8 Article 10.3390/polym6082274 2274 2286 2073-4360 2014-08-22 doi: 10.3390/polym6082274 Jeffrey Eisenhaure Seok Kim http://www.mdpi.com/2073-4360/6/8/2247 The increasing demand for greener and biodegradable materials leading to the satisfaction of society requires a compelling towards the advancement of nano-materials science. The polymeric matrix materials with suitable and proper filler, better filler/matrix interaction together with advanced and new methods or approaches are able to develop polymeric composites which shows great prospective applications in constructions and buildings, automotive, aerospace and packaging industries. The biodegradability of the natural fibers is considered as the most important and interesting aspects of their utilization in polymeric materials. Nanocomposite shows considerable applications in different fields because of larger surface area, and greater aspect ratio, with fascinating properties. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors, such as aerospace, automotive, electronics, and biotechnology industries. Hybrid bio-based composites that exploit the synergy between natural fibers in a nano-reinforced bio-based polymer can lead to improved properties along with maintaining environmental appeal. This review article intended to present information about diverse classes of natural fibers, nanofiller, cellulosic fiber based composite, nanocomposite, and natural fiber/nanofiller-based hybrid composite with specific concern to their applications. It will also provide summary of the emerging new aspects of nanotechnology for development of hybrid composites for the sustainable and greener environment. Polymers 2014-08-22 6 8 Review 10.3390/polym6082247 2247 2273 2073-4360 2014-08-22 doi: 10.3390/polym6082247 Naheed Saba Paridah Tahir Mohammad Jawaid http://www.mdpi.com/2073-4360/6/8/2232 The superlative mechanical properties of graphene-based materials make them the ideal filler materials for polymer composites reinforcement. Two types of graphene-based materials, graphene nanoplatelets (xGnP) and reduced graphene oxide (rGO), were used as nanofiller in poly(lactic acid) (PLA) polymer matrix, as well as plasticized PLA. The addition of rGO into PLA or plasticized PLA substantially enhanced the tensile strength without deteriorating elasticity, compared to xGnP nanocomposites. In addition, the investigation of the thermal properties has found that the presence of rGO in the system is very beneficial for improving thermal stability of the PLA or plasticized PLA. Scanning electron microscope (SEM) images of the rGO nanocomposites display homogenous and good uniformity morphology. Transmission electron microscopy (TEM) images revealed that the rGO remained intact as graphene sheet layers and were dispersed well into the polymer matrix, and it was confirmed by X-ray diffraction (XRD) results, which shows no graphitic peak in the XRD pattern. Polymers 2014-08-21 6 8 Article 10.3390/polym6082232 2232 2246 2073-4360 2014-08-21 doi: 10.3390/polym6082232 Buong Chieng Nor Ibrahim Wan Yunus Mohd Hussein Yoon Then Yuet Loo http://www.mdpi.com/2073-4360/6/8/2221 The objective of this research was to provide a useful approach of polymer synthesis for accelerating the fast cure of phenol-urea-formaldehyde (PUF) resin as wood adhesive by optimizing its structure and composition. The PUF resins containing high contents of very reactive groups such as para-methylol groups were synthesized by reacting methylolurea, phenol, and formaldehyde in the presence of magnesium oxide (MgO) as catalyst. The effects of synthesis parameters including F/(P + U), OH/P, and MgO/P mole ratios on the structure, composition, curing characteristics, and their relationships of PUF resins were investigated. The results indicated that MgO seemed to be an efficacious catalyst for PUF resin synthesis and promote its faster cure. The increase in the F/(P + U) mole ratio or/and OH/P mole ratio appeared to be beneficial for the formation of para-methylol groups and cocondensed methylene linkages between phenolic methylol groups and urea units, and for the removal of unreacted urea. In case of Catalyst/P mole ratio, an appropriate dosage of added metal-ion was very important for synthesizing the high-content reactive groups of PUF resins, otherwise leading to the reverse effects. Polymers 2014-08-20 6 8 Article 10.3390/polym6082221 2221 2231 2073-4360 2014-08-20 doi: 10.3390/polym6082221 Dong-Bin Fan Gai-Yun Li Te-Fu Qin Fu-Xiang Chu http://www.mdpi.com/2073-4360/6/8/2186 Polymer-drug conjugates have demonstrated clinical potential in the context of anticancer therapy. However, such promising results have, to date, failed to translate into a marketed product. Polymer-drug conjugates rely on two factors for activity: (i) the presence of a defective vasculature, for passive accumulation of this technology into the tumour tissue (enhanced permeability and retention (EPR) effect) and (ii) the presence of a specific trigger at the tumour site, for selective drug release (e.g., the enzyme cathepsin B). Here, we retrospectively analyse literature data to investigate which tumour types have proved more responsive to polymer-drug conjugates and to determine correlations between the magnitude of the EPR effect and/or expression of cathepsin B. Lung, breast and ovarian cancers showed the highest response rate (30%, 47% and 41%, respectively for cathepsin-activated conjugates and 31%, 43%, 40%, across all conjugates). An analysis of literature data on cathepsin content in various tumour types showed that these tumour types had high cathepsin content (up to 3835 ng/mg for lung cancer), although marked heterogeneity was observed across different studies. In addition, these tumour types were also reported as having a high EPR effect. Our results suggest that a pre-screening of patient population could bring a more marked clinical benefit. Polymers 2014-08-20 6 8 Article 10.3390/polym6082186 2186 2220 2073-4360 2014-08-20 doi: 10.3390/polym6082186 Amit Rajora Divyashree Ravishankar Helen Osborn Francesca Greco http://www.mdpi.com/2073-4360/6/8/2166 When non-covalently bonded crystalline inclusion compounds (ICs) are formed by threading the host cyclic starches, cyclodextrins (CDs), onto guest polymer chains, and excess polymer is employed, non-stoichiometric (n-s)-polymer-CD-ICs, with partially uncovered and "dangling" chains result. The crystalline host CD lattice is stable to ~300 °C, and the uncovered, yet constrained, portions of the guest chains emanating from the CD-IC crystal surfaces behave very distinctly from their neat bulk samples. In CD-IC crystals formed with α- and γ-CD hosts, each containing, respectively, six and eight 1,4-α-linked glucose units, the channels constraining the threaded portions of the guest polymer chains are ~0.5 and 1.0 nm in diameter and are separated by ~1.4 and 1.7 nm. This results in dense brushes with ~0.6 and 0.4 chains/nm2 (or 0.8 if two guest chains are included in each γ-CD channel) of the un-included portions of guest polymers emanating from the host CD-IC crystal surfaces. In addition, at least some of the guest chains leaving from a crystalline CD-IC surface re-enter another CD-IC crystal creating a network structure that leads to shape-memory behavior for (n-s)-polymer-CD-ICs. To some extent, (n-s)-polymer-CD-ICs can be considered as dense polymer brushes with chains that are tethered on both ends. Not surprisingly, the behavior of the un-included portions of the guest polymer chains in (n-s)-polymer-CD-ICs are quite different from those of their neat bulk samples, with higher glass-transition and melt crystallization temperatures and crystallinities. Here we additionally compare their behaviors to samples coalesced from their stoichiometric ICs, and more importantly to dense polymer brushes formed by polymer chains chemically bonded to surfaces at only one end. Judging on the basis of their glass-transition, crystallization and melting temperatures, and crystallinities, we generally find the un-included portions of chains in (n-s)-polymer-CD-ICs to be more constrained than those in neat bulk as-received and coalesced samples and in high density brushes. The last observation is likely because many of the un-included chain portions in (n-s)-polymer-CD-ICs are tethered/constrained at both ends, while the chains in their dense brushes are tethered at only one end. Polymers 2014-08-13 6 8 Review 10.3390/polym6082166 2166 2185 2073-4360 2014-08-13 doi: 10.3390/polym6082166 Alan Tonelli http://www.mdpi.com/2073-4360/6/8/2157 The release of insulin from insulin-containing CaCO3 microspheres was investigated. The microspheres were prepared by mixing aqueous solutions of CaCl2 and Na2CO3 in the presence of insulin. The surface of the insulin-containing CaCO3 microspheres was coated with a layer-by-layer thin film consisting of poly(allylamine hydrochloride) and poly(styrene sulfonate) to regulate the release kinetics of insulin. The release rate of insulin from the coated CaCO3 microspheres was significantly suppressed compared with that of uncoated CaCO3 microspheres, and depended on the thickness of the films. Rhombohedral calcite crystals of CaCO3 formed from the microspheres during the release of insulin, suggesting that the CaCO3 microspheres dissolved and recrystallized during the release of insulin. Polymers 2014-08-11 6 8 Communication 10.3390/polym6082157 2157 2165 2073-4360 2014-08-11 doi: 10.3390/polym6082157 Katsuhiko Sato Masaru Seno Jun-Ichi Anzai http://www.mdpi.com/2073-4360/6/8/2146 A novel all-polymeric blend with high dielectric constant (K) has been developed by blending polyvinylidene fluoride (PVDF) and polyamide (PA11) via co-melt-pressing technology with a compatilizer vinyl acetate-maleic anhydride (VA-MA) copolymer. Adding a copolymer of vinyl acetate and maleic anhydride decreased the dielectric loss (tan δ ≈ 0.057) and increased the dielectric constant (Kblend = 15). The blends show high dielectric constants, which give better frequency stability, and excellent mechanical properties. SEM investigations suggest that the enhanced dielectric behavior originates from significant interfacial polymer-polymer interactions. FT-IR, DSC and XRD demonstrate that blending PA11 with PVDF affects the crystalline behavior of each component. The high-K polymeric blends created represent a novel type of material that is flexible and easy to process, moreover, is appropriate for flexible micro-electronics. Polymers 2014-08-11 6 8 Article 10.3390/polym6082146 2146 2156 2073-4360 2014-08-11 doi: 10.3390/polym6082146 Dongliang Kuang Rui Li Jianzhong Pei http://www.mdpi.com/2073-4360/6/8/2116 Biocompatible and biodegradable block copolymers (BBCPs) containing crystalline blocks become increasingly important in polymer science, and have great potential applications in polymer materials. Crystallization in polymers is accompanied by the adoption of an extended conformation, or often by chain folding. It is important to distinguish between crystallization in homopolymers and in block copolymers. In homopolymers, chain folding leads to metastable structures introduced by the crystallization kinetics. In contrast, equilibrium chain folding in diblocks can be achieved as the equilibrium number of the folds is controlled by the size of the second block. The structures of BBCPs, which are determined by the competition between crystallization, microphase separation, kinetics and processing, have a tremendous influence on the final properties and applications. In this review, we present the recent advances on crystalline–crystalline diblock copolymer in our group. Polymers 2014-08-04 6 8 Review 10.3390/polym6082116 2116 2145 2073-4360 2014-08-04 doi: 10.3390/polym6082116 Feifei Xue Shichun Jiang http://www.mdpi.com/2073-4360/6/8/2100 The formation of polyelectrolyte multilayers (PEMs) for the first time, two decades ago, demonstrating the assembly on charged substrates in a very simple and efficient way, has proven to be a reliable method to obtain structures tunable at the nanometer scale. Much effort has been put into the assembly of these structures for their use in biological applications. A number of these efforts have been in combination with microfluidic systems, which add to the nanoassembly that is already possible with polyelectrolytes, a new dimension in the construction of valuable structures, some of them not possible with conventional systems. This review focuses on the advancements demonstrated by the combination of PEMs and microfluidic systems, and their use in biological applications. Polymers 2014-07-31 6 8 Review 10.3390/polym6082100 2100 2115 2073-4360 2014-07-31 doi: 10.3390/polym6082100 Saugandhika Minnikanti Aveek Gangopadhyay Darwin Reyes http://www.mdpi.com/2073-4360/6/8/2082 The surface alignment of liquid crystalline dendrimers (LCDrs) is a key factor for many of their potential applications. Here, we present results from Monte Carlo simulations of LCDrs adsorbed on flat, impenetrable aligning substrates. A tractable coarse-grained force field for the inter-dendritic and the dendrimer-substrate interactions is introduced. We investigate the conformational and ordering properties of single, end-functionalized LCDrs under homeotropic, random (or degenerate) planar and unidirectional planar aligning substrates. Depending on the anchoring constrains to the mesogenic units of the LCDr and on temperature, a variety of stable ordered LCDr states, differing in their topology, are observed and analyzed. The influence of the dendritic generation and core functionality on the surface-induced ordering of the LCDrs are examined. Polymers 2014-07-30 6 8 Article 10.3390/polym6082082 2082 2099 2073-4360 2014-07-30 doi: 10.3390/polym6082082 Zerihun Workineh Alexandros Vanakaras http://www.mdpi.com/2073-4360/6/7/2065 This paper discusses the long-term behavior of a series of highly-loaded, spun concrete pole specimens prestressed with carbon fiber-reinforced polymer (CFRP) tendons, which were subjected to outdoor four-point bending creep tests since 1996 in the frame of collaboration with the Swiss precast concrete producer, SACAC (Società Anonima Cementi Armati Centrifugati). The 2 m span cylindrical beams studied are models for lighting poles produced for the last 10 years and sold on the European market. Five thin-walled pole specimens were investigated (diameter: 100 mm; wall-thickness: 25–27 mm). All specimens were produced in a pretensioning and spinning technique and were prestressed by pultruded CFRP tendons. Initially, two reference pole specimens were tested in quasi-static four-point bending to determine the short-term failure moment and to model the short-term flexural behavior. Then, three pole specimens were loaded to different bending creep moments: while the lowest loaded specimen was initially uncracked, the second specimen was loaded with 50% of the short-term bending failure moment and exhibited cracking immediately after load introduction. The highest loaded pole specimen sustained a bending moment of 72% of the short-term bending failure moment for 16.5 years before failing in July 2013, due to the bond failure of the tendons, which led to local crushing of the high-performance spun concrete (HPSC). Besides this, long-term monitoring of the creep tests has shown a limited time- and temperature-dependent increase of the deflections over the years, mainly due to the creep of the concrete. A concrete creep-based model allowed for the calculation of the long-term bending curvatures with reasonable accuracy. Furthermore, the pole specimens showed crack patterns that were stable over time and minimal slippage of the tendons with respect to the pole's end-faces for the two lower load levels. The latter proves the successful and durable anchorage of these novel CFRP prestressing tendons in thin-walled, precast concrete members under realistic long-term service loads. Polymers 2014-07-23 6 7 Article 10.3390/polym6072065 2065 2081 2073-4360 2014-07-23 doi: 10.3390/polym6072065 Giovanni Terrasi Urs Meier Christian Affolter http://www.mdpi.com/2073-4360/6/7/2051 This work deals with the development of a mechanics-based shear model for reinforced concrete (RC) elements strengthened in shear with fiber-reinforced polymer (FRP) and a design/assessment procedure capable of predicting the failure sequence of resisting elements: the yielding of existing transverse steel ties and the debonding of FRP sheets/strips, while checking the corresponding compressive stress in concrete. The research aims at the definition of an accurate capacity equation, consistent with the requirement of the pseudo-ductile shear behavior of structural elements, that is, transverse steel ties yield before FRP debonding and concrete crushing. For the purpose of validating the proposed model, an extended parametric study and a comparison against experimental results have been conducted: it is proven that the common accepted rule of assuming the shear capacity of RC members strengthened in shear with FRP as the sum of the maximum contribution of both FRP and stirrups can lead to an unsafe overestimation of the shear capacity. This issue has been pointed out by some authors, when comparing experimental shear capacity values with the theoretical ones, but without giving a convincing explanation of that. In this sense, the proposed model represents also a valid instrument to better understand the mechanical behavior of FRP-RC beams in shear and to calculate their actual shear capacity. Polymers 2014-07-18 6 7 Article 10.3390/polym6072051 2051 2064 2073-4360 2014-07-18 doi: 10.3390/polym6072051 Floriana Petrone Giorgio Monti http://www.mdpi.com/2073-4360/6/7/2037 This article reports about nanocomposites, which refractive index is tuned by adding TiO2 nanoparticles. We compare in situ/ex situ preparation of nanocomposites. Preparation procedure is described, properties of nanocomposites are compared, and especially we examine the applicability of two-photon polymerization (2PP) of synthesized nanocomposites. All prepared samples exhibit suitable optical transparency at specific laser wavelengths. Three-dimensional structures were generated by means of two-photon polymerization effect induced by a femtosecond laser. Polymers 2014-07-14 6 7 Article 10.3390/polym6072037 2037 2050 2073-4360 2014-07-14 doi: 10.3390/polym6072037 Qingchuan Guo Reza Ghadiri Thomas Weigel Andreas Aumann Evgeny Gurevich Cemal Esen Olaf Medenbach Wei Cheng Boris Chichkov Andreas Ostendorf http://www.mdpi.com/2073-4360/6/7/2018 Thin casein films for food packaging applications reportedly possess good strength and low oxygen permeability, but low elasticity and high sensitivity to moisture. Modifying the films to target specific behaviors depending on environmental conditions can enable a variety of commercial applications for casein-based films. The mechanical properties of solvent-cast (15% solids) calcium-caseinate/glycerol films (CaCas:Gly ratio of 3:1) were characterized as a function of processing and environmental conditions, including film thickness, solution formulation and ambient humidity (from 22% to 70% relative humidity (RH) at ~20 °C). At constant RH, the elongation at break (EAB) had a strong positive dependence on the film thickness. When RH increased, the tensile strength (TS) and modulus (E) decreased approximately linearly, while EAB increased. From 0.05% to 1% (w/w) of citric pectin (CP) was then incorporated into CaCas/Gly films following seven different formulations (mixing sequences), to alter the protein network and to evaluate the effects of CP on the tensile properties of CaCas/Gly/CP films. At constant film thickness and ~60% RH, the addition of 0.1% or 1.0% CP to the films considerably increased or decreased EAB, TS and E in different directions and to different extents, depending on the formulation, while optical micrographs also showed vastly differing network configurations, suggesting complex formulation- and stoichiometry-dependent casein-pectin interactions within the dried films. Depending on the desired film properties and utilization conditions, pectin may be a useful addition to casein film formulations for food packaging applications. Polymers 2014-07-14 6 7 Article 10.3390/polym6072018 2018 2036 2073-4360 2014-07-14 doi: 10.3390/polym6072018 Laetitia Bonnaillie Han Zhang Serife Akkurt Kit Yam Peggy Tomasula http://www.mdpi.com/2073-4360/6/7/1999 Polyelectrolytes in dilute solutions (0.01 mmol/L) adsorb in a two-dimensional lamellar phase to oppositely charged lipid monolayers at the air/water interface. The interchain separation is monitored by Grazing Incidence X-ray Diffraction. On monolayer compression, the interchain separation decreases to a factor of two. To investigate the influence of the electrostatic interaction, either the line charge density of the polymer is reduced (a statistic copolymer with 90% and 50% charged monomers) or mixtures between charged and uncharged lipids are used (dipalmitoylphosphatidylcholine (DPPC)/ dioctadecyldimethylammonium bromide (DODAB)) On decrease of the surface charge density, the interchain separation increases, while on decrease of the linear charge density, the interchain separation decreases. The ratio between charged monomers and charged lipid molecules is fairly constant; it decreases up to 30% when the lipids are in the fluid phase. With decreasing surface charge or linear charge density, the correlation length of the lamellar order decreases. Polymers 2014-07-10 6 7 Article 10.3390/polym6071999 1999 2017 2073-4360 2014-07-10 doi: 10.3390/polym6071999 Thomas Ortmann Heiko Ahrens Sven Milewski Frank Lawrenz Andreas Gröning André Laschewsky Sebastien Garnier Christiane Helm http://www.mdpi.com/2073-4360/6/7/1972 This work reports the outcomes of an extensive experimental campaign on the retrofitting of masonry walls by means of carbon fiber reinforced polymer (CFRP) sheets, carried out at University of Applied Sciences (UAS) Fribourg. In the first stage, static-cyclic shear tests were conducted on the masonry walls, followed by a second stage of tensile tests on alternative configurations of mechanical anchorage so as to assess the effects on the structural response and to identify the associated limits. In the static-cyclic shear tests, it was found that the resistance of masonry walls retrofitted with CFRP sheets was improved by up to 70%, and the deformability was improved by up to 10% in comparison to the un-retrofitted specimens. The experimental tests conducted on alternate configurations of mechanical anchorages indicate that the tested materials and configurations rely heavily on details. The sensitivity of CFRP sheets to edges, non-uniformities on any adherend, and bonding defects can cause premature CFRP failure and, hence, pose problems for the efficient design of a retrofitting scheme. As indicated by the results of this investigation, effective anchorage can be achieved when eccentric loading of the mechanical anchorage is avoided and a smooth bonding surface is guaranteed. Polymers 2014-07-10 6 7 Article 10.3390/polym6071972 1972 1998 2073-4360 2014-07-10 doi: 10.3390/polym6071972 Patrick Bischof René Suter Eleni Chatzi Pierino Lestuzzi http://www.mdpi.com/2073-4360/6/7/1958 A novel gel undergoes the Belousov-Zhabotinsky (BZ) reaction in strong-acid-free conditions. Under such conditions, the gel can switch the BZ reaction on or off in conventional self-oscillating gels that undergo self-oscillation only in aqueous solutions with strong acids, such as HNO3 or H2SO4. The self-oscillation of the polymer chain can be controlled by varying the temperature, owing to its thermoresponsive property. Moreover, the polymer chain undergoes viscosity self-oscillations in strong-acid-free conditions. In this review, the direct observation of self-oscillations in polymer chains attached to glass or gold surfaces, by using scanning probe microscopy and quartz crystal microbalances with dissipation monitoring, is discussed. Polymers 2014-07-09 6 7 Review 10.3390/polym6071958 1958 1971 2073-4360 2014-07-09 doi: 10.3390/polym6071958 Yusuke Hara http://www.mdpi.com/2073-4360/6/7/1948 In this paper, we propose the evaluation of the mannitol's ability to reduce hyaluronic acid (HA) degradation using two different models of oxidative stress. Firstly, a solution of hyaluronan and a solution of the same HA including mannitol in PBS buffer were submitted to an oxidative stress generated by the addition of xanthine + xanthine oxidase generating oxygen free radicals. Different enzyme concentrations were used and the HA properties were studied after 24 h of contact at ambient temperature. Decreases of the viscosity of the solution were assessed by rheometry (viscous and elastic module) and that of HA molecular weight was determined by steric exclusion chromatography. Rheologic behavior was assessed on identical HA solutions subjected to another model of oxidative stress imposed by addition of hydrogen peroxide. The influence of mannitol concentration on HA degradation was also demonstrated. Whatever the stress applied, it appears very clearly that mannitol protects hyaluronic acid from mediated oxygen free radicals degradation. These in vitro results suggest that mannitol could be a simple way to significantly increase the intra-articular residence time of the injected hyaluronic acid and therefore might improve viscosupplementation effectiveness. Polymers 2014-07-08 6 7 Article 10.3390/polym6071948 1948 1957 2073-4360 2014-07-08 doi: 10.3390/polym6071948 Marguerite Rinaudo Bernard Lardy Laurent Grange Thierry Conrozier http://www.mdpi.com/2073-4360/6/7/1929 This work deals with the influence of functionalization degree on the thermogravimetric and rheological behaviour of NCO-functionalized chitosan- and chitin-based oleogels. Chitosan and chitin were functionalized using different proportions of 1,6-hexamethylene diisocyanate (HMDI) and subsequently dispersed in castor oil to promote the chemical reaction between the –NCO group of the modified biopolymer and the –OH group located in the ricinoleic fatty acid chain of castor oil, thus resulting in different oleogels with specific thermogravimetric and rheological characteristics. Biopolymers and oleogels were characterized through Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Small-amplitude oscillatory shear (SAOS) measurements were performed on the oleogels. Oleogels presented suitable thermal resistance, despite the fact that the inclusion of HMDI moieties in the polymer structure led to a reduction in the onset temperature of thermal degradation. The insertion of low amounts of HMDI in both chitin and chitosan produces a drastic reduction in the values of oleogel viscoelastic functions but, above a critical threshold, they increase with the functionalization degree so that isocyanate functionalization results in a chemical tool to modulate oleogel rheological response. Several NCO-functionalized chitosan- and chitin-based oleogel formulations present suitable thermal resistance and rheological characteristics to be proposed as bio-based alternatives to traditional lubricating greases. Polymers 2014-07-08 6 7 Article 10.3390/polym6071929 1929 1947 2073-4360 2014-07-08 doi: 10.3390/polym6071929 Rocío Gallego Mercedes González Jesús Arteaga Concepción Valencia José Franco http://www.mdpi.com/2073-4360/6/7/1914 With the classical sulfonation method of polystyrene-based strongly acidic cation exchange resins, polystyrene/polyvinylidene fluoride (PVDF) alloy particles were sulfonated to obtain a cation exchange resin, which was then directly thermoformed to prepare a semi-interpenetrating polymer network (semi-IPN) cation exchange membrane. The effects of the swelling agent, sulfonation time and temperature and the relative contents of polystyrene and divinylbenzene (DVB) in the alloy particles on the feasibility of the membrane formation are discussed. The results indicate that a favorable sulfonation degree above 80% and a suitable ion exchange capacity of 1.5–2.4 mmol/g can be gained, with concentrated sulfuric acid as the sulfonation agent and 1,2-dichloroethane as the swelling agent. The running electrical resistance and desalination effect of the prepared cation exchange membrane were measured in a pilot-scale electrodialyser and not only obviously exceeded a commercial heterogeneous cation exchange membrane, but was also very close to a commercial homogenous membrane. In this way, the authors have combined the classical sulfonation method of polystyrene-based cation exchange resins with the traditional thermoforming manufacturing process of heterogeneous cation exchange membranes, to successfully develop a novel, low-price, but relatively high-performance polystyrene/PVDF cation exchange membrane with the semi-IPN structure. Polymers 2014-07-07 6 7 Article 10.3390/polym6071914 1914 1928 2073-4360 2014-07-07 doi: 10.3390/polym6071914 Yin-lin Lei Yun-jie Luo Fei Chen Le-he Mei http://www.mdpi.com/2073-4360/6/7/1897 Abstract: We present results of the hybrid Monte Carlo/molecular dynamics simulations of the osmotic pressure of salt solutions of polyelectrolytes. In our simulations, we used a coarse-grained representation of polyelectrolyte chains, counterions and salt ions. During simulation runs, we alternate Monte Carlo and molecular dynamics simulation steps. Monte Carlo steps were used to perform small ion exchange between simulation box containing salt ions (salt reservoir) and simulation box with polyelectrolyte chains, counterions and salt ions (polyelectrolyte solution). This allowed us to model Donnan equilibrium and partitioning of salt and counterions across membrane impermeable to polyelectrolyte chains. Our simulations have shown that the main contribution to the system osmotic pressure is due to salt ions and osmotically active counterions. The fraction of the condensed (osmotically inactive) counterions first increases with decreases in the solution ionic strength then it saturates. The reduced value of the system osmotic coefficient is a universal function of the ratio of the concentration of osmotically active counterions and salt concentration in salt reservoir. Simulation results are in a very good agreement with osmotic pressure measurements in sodium polystyrene sulfonate, DNA, polyacrylic acid, sodium polyanetholesulfonic acid, polyvinylbenzoic acid, and polydiallyldimethylammonium chloride solutions. Polymers 2014-07-04 6 7 Article 10.3390/polym6071897 1897 1913 2073-4360 2014-07-04 doi: 10.3390/polym6071897 Jan-Michael Carrillo Andrey Dobrynin http://www.mdpi.com/2073-4360/6/7/1877 The effect of brush thickness on the loading of gold nanoparticles (AuNPs) within stimuli-responsive poly-(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) polyelectrolyte brushes is reported. Atom transfer radical polymerization (ATRP) was used to grow polymer brushes via a "grafting from" approach. The brush thickness was tuned by varying the polymerization time. Using a new type of sealed reactor, thick brushes were synthesized. A systematic study was performed by varying a single parameter (brush thickness), while keeping all other parameters constant. AuNPs of 13 nm in diameter were attached by incubation. X-ray reflectivity, electron scanning microscopy and ellipsometry were used to study the particle loading, particle distribution and interpenetration of the particles within the brush matrix. A model for the structure of the brush/particle hybrids was derived. The particle number densities of attached AuNPs depend on the brush thickness, as do the optical properties of the hybrids. An increasing particle number density was found for increasing brush thickness, due to an increased surface roughness. Polymers 2014-06-27 6 7 Article 10.3390/polym6071877 1877 1896 2073-4360 2014-06-27 doi: 10.3390/polym6071877 Stephanie Christau Stefan Thurandt Zuleyha Yenice Regine von Klitzing http://www.mdpi.com/2073-4360/6/6/1862 Combining the advantages of basalt fiber-reinforced polymer (BFRP) material and steel material, a novel BFRP-steel composite plate (BSP) is proposed, where a steel plate is sandwiched between two outer BFRP laminates. The main purpose of this research is to investigate the mechanical behavior of the proposed BSP under uniaxial tension and cyclic tension. Four groups of BSP specimens with four different BFRP layers and one control group of steel plate specimens were prepared. A uniaxial tensile test and a cyclic tensile test were conducted to determine the initial elastic modulus, postyield stiffness, yield strength, ultimate bearing capacity and residual deformation. Test results indicated that the stress-strain curve of the BSP specimen was bilinear prior to the fracture of the outer BFRP, and the BSP specimen had stable postyield stiffness and small residual deformation after the yielding of the inner steel plate. The postyield modulus of BSP specimens increased almost linearly with the increasing number of outer BFRP layers, as well as the ultimate bearing capacity. Moreover, the predicted results from the selected models under both monotonic tension and cyclic tension were in good agreement with the experimental data. Polymers 2014-06-23 6 6 Article 10.3390/polym6061862 1862 1876 2073-4360 2014-06-23 doi: 10.3390/polym6061862 Yunyu Li Yanlei Wang Jinping Ou http://www.mdpi.com/2073-4360/6/6/1846 Poly(p-phenylene terephtalamide) (PPTA), a high-performance polymer with high modulus and good hydrophilicity, is often used as a reinforced material. However, due to its high crystallity, micro-phase separation often occurs in the blends. In this paper, PPTA/poly(vinylidene fluoride) (PVDF) compatible blend solution was synthesized by in situ polycondensation. Blend ultra-filtration membrane was prepared through the immersion phase inversion process. In order to obtain desired pore structure, the effects of different additives including hydrophilic polymer (polyethylene glycol (PEG)), inorganic salt (lithium chloride (LiCl)) and the surfactant (Tween-80) on the morphology and performance of PPTA/PVDF blend membranes were studied. The membrane formation process was investigated through ternary phase diagram (thermodynamics) and viscosities (kinetics) analysis. It was found that, with the increasing of LiCl content, a porous membrane structure with long finger-like pores was formed due to the accelerated demixing process which resulted in the increase of porosity and pore diameter as well as the enhancement of water flux and the decline of PEG rejection. When Tween content increased to over 3 wt%, dynamic viscosity became the main factor resulting in a decreased phase separation rate. The transfer of PEG and LiCl molecules onto membrane surface increased the surface hydrophilicity. The effect of Tween content on membrane hydrophilicity was also correlated with the compatibility of blend components. Polymers 2014-06-20 6 6 Article 10.3390/polym6061846 1846 1861 2073-4360 2014-06-20 doi: 10.3390/polym6061846 Hong-Bin Li Wen-Ying Shi Yu-Feng Zhang Dong-Qing Liu Xiao-Feng Liu http://www.mdpi.com/2073-4360/6/6/1827 In this study, we investigated the self-assembly of two homopolymers of the same molecular weight, but containing complementary nucleobases. After employing nitroxide-mediated radical polymerization to synthesize poly(vinylbenzyl chloride), we converted the polymer into poly(vinylbenzyl azide) through a reaction with NaN3 and then performed click chemistry with propargyl thymine and propargyl adenine to yield the homopolymers, poly(vinylbenzyl triazolylmethyl methylthymine) (PVBT) and poly(vinylbenzyl triazolylmethyl methyladenine) (PVBA), respectively. This PVBT/PVBA blend system exhibited a single glass transition temperature over the entire range of compositions, indicative of a miscible phase arising from the formation of multiple strong complementary hydrogen bonds between the thymine and adenine groups of PVBT and PVBA, respectively; Fourier transform infrared and 1H nuclear magnetic resonance spectroscopy confirmed the presence of these noncovalent interactions. In addition, dynamic rheology, dynamic light scattering and transmission electron microscopy provided evidence for the formation of supramolecular network structures in these binary PVBT/PVBA blend systems. Polymers 2014-06-18 6 6 Article 10.3390/polym6061827 1827 1845 2073-4360 2014-06-18 doi: 10.3390/polym6061827 Yu-Shian Wu Yi-Chen Wu Shiao-Wei Kuo http://www.mdpi.com/2073-4360/6/6/1810 For the last three decades, fiber reinforced polymer (FRP) composite materials have been widely used in major engineering industries. Managing FRP waste is becoming an important issue due to the growth in the production of FRP composite materials. In this article, the issue of FRP waste management is discussed and the commonly used methods for the handling of FRP waste are reviewed. One potentially viable use of FRP waste is in the partial replacement of fillers or aggregates in cementitious materials (particularly portland cement mortar and concrete). A number of important prior investigations performed on the use of FRP waste in concrete and mortar are reviewed. The results from most of those investigations suggest that FRP aggregates significantly reduce the strength of cementitious materials with little significant effect on durability. Recommendations for future research in this area are provided for producing stronger mortars and concretes incorporating FRP production and end-of-life waste. Polymers 2014-06-17 6 6 Review 10.3390/polym6061810 1810 1826 2073-4360 2014-06-17 doi: 10.3390/polym6061810 Ardavan Yazdanbakhsh Lawrence Bank