Synthesis and properties of poly(ethylene oxide)‐grafted polyethylene copolymer and terpolymer

A series of graft copolymers were synthesized based on ethylene‐co‐m,p‐methylstyrene (EMS) (backbone copolymer), ethylene‐1‐hexene‐m,p‐methylstyrene (EHMS) (backbone terpolymer), and polyethylene glycol monomethyl ethers (PEGM) (grafts) in this study. The PEGMs with molecular weights of 750 and 2000 were used. The chemical composition of the graft copolymers was analyzed by NMR and DSC measurements. The graft copolymers exhibited a phase‐separated morphology with the backbone and the methoxy polyethylene glycol (MPEG) grafts forming separate crystalline phases. The MPEG phase had a melting temperature lower than the corresponding MPEG homopolymer, as determined by DSC. The melting point of the crystalline phase formed by the EMS and EHMS main chains was lower than that of pure polymer backbone. Copyright © 2009 John Wiley & Sons, Ltd.     

Locating and capacity planning for retailers of a new supply chain to compete on the plane

This paper investigates the network design problem of a two-level supply chain (SC), which is applicable for industries such as automotive, fuel and tyre manufacturing. Models presented in this paper aim at locating retail facilities of an SC and identifying their required capacities in the presence of existing competing retailers of a rival SC. We consider feasible locating space of the retail facilities on the continuous plane with bounded constraints and static competition among the rivals of the markets with deterministic demands. The problem is used for both essential and luxury product cases; hence, we consider elastic and inelastic demands, both. The models discussed in this paper are non-linear and non-convex which are difficult to solve. We use interval branch-and-bound as optimization algorithm for small size single-retailer problems, but for large-scale, multi-retailer problems we need to have more efficient methods. Therefore, we apply a heuristic algorithm (H1), a simulated annealing (SA) algorithm, an interior point (IP) algorithm, a genetic algorithm (GA) and a pattern search algorithm for solving multi-retailer problem with elastic and inelastic demands. Computational results obtained from performing different solution approaches for both elastic and inelastic show that mostly IP, PS, and H1 methods outperform the other approaches. The computational results on a real-life case are also promising. Several extended mathematical models and an example of a typical case with details are presented in the appendices of the paper.     

Hydrogen sensors based on conductivity changes in polyaniline nanofibers

Hydrogen causes a reversible decrease in the resistance of a thin film of camphorsulfonic acid doped polyaniline nanofibers. For a 1% mixture of hydrogen in nitrogen, a 3% decrease in resistance is observed (DeltaR/R = -3%). The hydrogen response is completely suppressed in the presence of humidity. In contrast, oxygen does not inhibit the hydrogen response. A deuterium isotope effect on the sensor response is observed in which hydrogen gives a larger response than deuterium: (DeltaR/R)H/(DeltaR/R)D = 4.1 +/- 0.4. Mass sensors using nanofiber films on a quartz crystal microbalance also showed a comparable deuterium isotope effect: DeltamH/DeltamD = 2.3 +/- 0.2 or DeltanH/DeltanD = 4.6 +/- 0.4 on a molar basis. The resistance change of polyaniline nanofibers is about an order of magnitude greater than conventional polyaniline, consistent with a porous, high-surface-area nanofibrillar film structure that allows for better gas diffusion into the film. A plausible mechanism involves hydrogen bonding to the amine nitrogens along the polyaniline backbone and subsequent dissociation. The inhibitory effect of humidity is consistent with a stronger interaction of water with the polyaniline active sites that bind to hydrogen. These data clearly demonstrate a significant interaction of hydrogen with doped polyaniline and may be relevant to recent claims of hydrogen storage by polyaniline.     

Vitamin B12 supported on graphene oxide: As a bio‐based catalyst for selective aerobic oxidation of alcohols

The environmental impact of chemical processes has now opened new windows of opportunity for bio‐based catalysts. In this paper a highly active bio‐based catalyst of vitamin B₁₂ supported on graphene oxide nanosheets is reported for the selective aerobic oxidation of alcohols to the corresponding carbonyl compounds. Operational simplicity, mild reaction conditions, high yield and selectivity, non‐hazardous nature, commercial availability and affordability are the main advantages of this novel catalytic system.     

A theoretical practice on grazing‐exit energy dispersive X‐ray spectroscopy as a surface analysis strategy to investigate BiVO4 nano‐films

In the current work, a thin film of bismuth vanadate was defined over a silicon substrate, and a calculative Monte Carlo approach was followed to achieve the best grazing‐exit angle to acquire compositional data from top few nanometers of surface. This strategy is very beneficial in order to increase X‐ray signals originated from surface and diminish the background X‐ray signals started off from the substrate. In this regard, grazing‐exit energy dispersive X‐ray spectroscopy can be considered as an accessible and economical analytical tool to investigate thin films and nano‐layers. The major advantage of this method is that just by applying a re‐arrangement in a scanning electron microscope, it can be used to study compositional properties of thin layers. In this contribution, a theoretical approach using Monte Carlo models was used to simulate the behavior of electron beams impinging onto BiVO₄ nano‐layers with thickness of 50 nm and electron trajectories inside the film. Characteristic X‐rays and spatial energy distribution of the backscattered electrons were also calculated. Under grazing‐exit angle of around 0.5°, the best surface signal/background noise ratio was achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of functional polyethylene graft copolymers by nitroxide‐mediated living radical polymerization

This paper describes a new method to prepare graft copolymers, such as polyethylene‐g‐polystyrene (PE‐g‐PS), with a relatively well‐controlled reaction mechanism. The chemistry involves a transformation process from the metallocene copolymerization of ethylene and m,p‐methylstyrene (m,p‐MS) to nitroxide‐mediated “living” free radical polymerization (LRFP) of styrene. The metallocene catalysis produces ethylene‐co‐m,p‐methylstyrene (EMS) random copolymers. Next, 1‐hydroxyl‐2,2,6,6‐tetramethylpiperidine (HO‐TEMPO) was synthesized by the reduction of TEMPO with sodium ascorbate. The macroinitiator (EMS‐TEMPO) was synthesized with the bromination reaction of EMS, and the following nucleofilic reaction with this functional nitroxyl compound. The resulting macroinitiator (EMS‐TEMPO) for LRFP was then heated in the presence of styrene to form graft copolymer. DSC, ¹H‐NMR, FTIR spectroscopy were employed to investigate the structure of the polymers. The results of Molau test showed that PE‐g‐PS could be a potential good compatilizer. Copyright © 2008 John Wiley & Sons, Ltd.     

Advances in Biohybridized Planar Polymer Membranes and Membrane-Like Matrices

The past few decades have seen increasing growth in the field of biomimetic membranes and thus also a rapid expansion of their biomedical and technological applications. Versatility, stability and scalability have moved biohybrid polymer membranes into the limelight. This review focuses on planar, soft polymer membranes and polymer-based matrices and their role as a host for different types of biomolecules. Because biomimetic polymer platforms present an extensive, ever-growing field, we limit ourselves mostly to the discussion of producing planar polymer membranes on solid supports that lend themselves to functionalization by biomolecules. We present an overview of the major highlights and challenges associated with the biohybridization of such polymer platforms. In particular, we elaborate on procedures developed to maintain optimal peptide and membrane protein performance in a customized polymer membrane or membrane-like environment. Finally, we discuss a number of applications of such biohybridized polymer platforms and contemplate future developments to further exploit their potential.     

Solitary wave solutions of coupled boussinesq equation

This article presents the general case‐study of our previous works regarding generalized Boussinesq equations [17, 18, 19], that focus on application of various subordinate methods where are applied to construct more general exact solutions of the coupled Boussinesq equations. In this article, the ‐expansion method is applied on coupled Boussinesq equations. Our work is motivated by the fact that the ‐expansion method provides not only more general forms of solutions but also periodic, solitary waves, and rational solutions. The method appears to be easier and faster by means of a symbolic manipulation program. © 2016 Wiley Periodicals, Inc. Complexity 21: 151–155, 2016     

Fluorescent Indolo[3,2-a]phenazines against Toxoplasma gondii: Concise Synthesis by Gold-Catalyzed Cycloisomerization with 1,2-Silyl Migration and ipso-Iodination Suzuki Sequence

A gold-catalyzed cycloisomerization of 2-indolyl-3-[(trimethylsilyl)ethynyl)]quinoxalines with concomitant 1,2-silyl shift forms 6-(trimethylsilyl)indolo[3,2-a]phenazines in moderate to excellent yield. These silylated heterocycles are readily transformed into 6-aryl-indolo[3,2-a]phenazines in moderate to good yield by one-pot ipso-iodination Suzuki coupling. The title compounds represent a novel type of tunable luminophore. Structure-property relationships for 6-aryl-indolo[3,2-a]phenazines obtained from Hammett correlations with σ_p+ substituent parameters indicate that emission maxima, Stokes shifts, and fluorescence quantum yields can be fine-tuned by the remote para-aryl substituent. Furthermore, indolo[3,2-a]phenazines were found to exhibit interesting activities against medically relevant pathogens such as the Apicomplexa parasite Toxoplasma gondii with an IC₅₀ of up to 0.67±0.13 μM. Thus, these compounds are promising candidates for novel anti-parasitic therapies.