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961.
Fatemeh Jahanbakhsh 《Liquid crystals》2013,40(10):1485-1493
ABSTRACTThe impact of varying the co-doping concentration of a mesogenic and a non-mesogenic monomer in the reactive mixtures used to create a copolymer network LCs was investigated. Use of copolymer has been found to improve the response properties in the obtained liquid crystal composites. The polymer network in the studied copolymer network LCs was examined by scanning electron microscopy and the response times in various samples were investigated. Samples were prepared with various reactive mixtures, each of which had a constant concentration of mesogenic monomer, various concentrations of non-mesogenic monomer, and the same amount of photoinitiator. These reactive mixtures were filled in home assembled test cells with planar alignment and then exposed to UV light. With increasing concentration of the non-mesogenic monomer, the response properties of the resulting copolymer network LC were improved. Usually, if the overall polymer content in a polymer network LC is increased, the threshold voltage is also increased. However, both threshold voltages and response times were lowered and the response properties were thus improved in the studied copolymer network LCs. This unexpected behavior could be traced back to inducing a grainy polymer morphology of the copolymer network by using a non-mesogenic monomer. 相似文献
962.
Fiona Regan Fiona Walsh James Walsh 《International journal of environmental analytical chemistry》2013,93(7-8):621-631
A novel plasticised PVC polymer membrane as a sensing film for the determination of BTEX compounds using ATR-FTIR spectroscopy is demonstrated. A range of 10 plasticised PVC phases have been investigated using toluene and tetrachloroethylene as test analytes. Both analyte enrichment rates and infrared absorbance values were considered when choosing a suitable polymer for sensing. An enhancement in analyte absorbance at the characteristic IR absorption bands was noted as the plasticiser concentration in the film was increased. 2% PVC with 75% diisooctyl azelate was found to show promising results for simultaneous determination of the BTEX compounds. All BTEX analytes can be measured in less than 8 min. A study of a multicomponent sample demonstrated that analyte enrichment times were influenced by the presence of even one additional analyte component in the sample. 相似文献
963.
A novel kind of sandwiched polymer membrane was prepared, which consists of two outer layers of electrospun poly(vinyl difluoride) (PVDF) fibrous films and one inner layer of poly(methyl methacrylate) (PMMA) film. Its characteristics were investigated by scanning electron microscopy and X-ray diffraction. The membrane can easily absorb non-aqueous electrolyte to form gelled polymer electrolytes (GPEs). The resulting gelled polymer electrolytes had a high ionic conductivity up to 1.93 × 10−3 S cm−1 at room temperature, and exhibited a high electrochemical stability potential of 4.5 V (vs. Li/Li+). It is of great potential application in polymer lithium-ion batteries. 相似文献
964.
965.
Haydaruzzaman Ruhul A. Khan Mubarak A. Khan A.H. Khan M.A. Hossain 《Radiation Physics and Chemistry》2009,78(11):986-993
Jute fabrics-reinforced polypropylene (PP) composites (50% fiber) were prepared by compression molding. Composites were fabricated with non-irradiated jute fabrics/non-irradiated PP (C-0), non-irradiated jute fabrics/irradiated PP (C-1), irradiated jute fabrics/non-irradiated PP (C-2) and irradiated jute fabrics/irradiated PP (C-3). It was found that C-3 composite performed the best mechanical properties over other composites. Total radiation dose varied from 250–1000 krad and composites made of using 500 krad showed the best results. The optimized values (C-3 composites) for tensile strength (TS), bending strength (BS) and impact strength (IS) were found to be 63 MPa, 73 MPa and 2.93 kJ/m2, respectively. 相似文献
966.
Chitosan–poly(vinyl alcohol), CS–PVA, blended membranes were prepared by solution casting of varying proportions of CS and PVA. The blend membranes were then crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The physiochemical properties of the blend membranes were determined using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), tensile test and contact angle measurements. Results from ATR-FTIR show that TMC has crosslinked the blend membranes successfully, and results of XRD and DSC show a corresponding decrease in crystallinity and increase in melting point, respectively. The crosslinked CS–PVA blend membranes also show improved mechanical strength but lower flexibility in tensile testing as compared to uncrosslinked membranes. Contact angle results show that crosslinking has decreased the surface hydrophilicity of the blend membranes. The blend membrane properties, including contact angle, melting point and tensile strength, change with a variation in the blending ratio. They appear to reach a maximum when the CS content is at 75 wt%. In general, the crosslinked blend membranes show excellent stability during the pervaporation (PV) dehydration of ethylene glycol–water mixtures (10–90 wt% EG) at different temperatures (25–70 °C). At 70 °C, for 90 wt% EG in the feed mixture, the crosslinked blend membrane with 75 wt% CS shows the highest total flux of 0.46 kg/(m2 h) and best selectivity of 986. The blending ratio of 75 wt% CS is recommended as the optimized ratio in the preparation of CS–PVA blend membranes for pervaporation dehydration of ethylene glycol. 相似文献
967.
With the many possible composition combinations possible for copolymers there is a critical need to develop methods of predicting the properties of these materials. This paper examines the applicability of popular, current vapor–liquid equilibria prediction models in characterizing the solubility of solvents in copolymers. In some cases anomalous behavior is observed where the solubility of the solvent in the copolymer is greater than or less than in either of the composite homopolymers. Two popular UNIFAC models and the group-contribution, lattice-fluid equation of state (GCLF-EoS) have been evaluated for this application. In general the UNIFAC models showed a better capability than the GCLF-EoS. There is a need for more sophisticated methods for predicting the complex interactions that can be present in copolymer systems. 相似文献
968.
Kazuhiko Kitano Yuuki Inoue Ryosuke Matsuno Madoka Takai Kazuhiko Ishihara 《Colloids and surfaces. B, Biointerfaces》2009,74(1):350-357
For preparing a “highly lubricated biointerface”, which has both excellent lubricity and biocompatibility, we investigated the factors responsible for resistance to friction during polymer grafting. We prepared poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(methyl methacrylate) (PMMA) brush layers with high graft density and well-controlled thickness using atom transfer radical polymerization (ATRP). We measured the water absorptivity in the polymer brush layers and the viscoelasticity of the polymer-hydrated layers using a quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The PMPC brush layer had the highest water absorptivity, while the PMPC-hydrated layer had the highest fluidity. The friction properties of the polymer brush layers were determined in air, water, and toluene by atomic force microscopy (AFM). The friction on each polymer brush decreased only when a good solvent was chosen for each polymer. In conclusion, the brush layer possessing high water absorptivity and fluidity in water contributes to reduce friction. PMPC grafting is an effective and promising method for obtaining highly lubricated biointerfaces. 相似文献
969.
We consider directed path models of a selection of polymer and vesicle problems. Each model is used to illustrate an important
method of solving lattice path enumeration problems. In particular, the Temperley method is used for the polymer collapse
problem. The ZL method is used to solve the semi-continuous vesicle model. The Constant Term method is used to solve a set
of partial difference equations for the polymer adsorption problem. The Kernel method is used to solve the functional equation
that arises in the polymer force problem. Finally, the Transfer Matrix method is used to solve a problem in colloid dispersions.
All these methods are combinatorially similar as they all construct equations by considering the action of adding an additional
column to the set of objects. 相似文献
970.
以膦酸酯聚芴为阴极界面修饰层, 高功函金属铝为阴极, 制备了一种高效聚合物红光电致发光器件. 通过X射线光电子能谱(XPS)的表征, 分析了经真空蒸镀沉积在膦酸酯聚芴表面的Al原子与下层的膦酸酯聚芴在有机物-金属界面处的作用情况, 结果表明, 在真空蒸镀金属Al的过程中, 在有机物-金属界面处形成了一种氧/铝复合物. 研究了这种氧/铝复合物对器件光电性能的影响, 结果表明, 氧/铝复合物的产生提高了阴极电子的注入, 使器件效率得到了很大提高. 与以Ca/Al为阴极的传统器件相比, 以膦酸酯聚芴/Al为阴极的聚合物电致发光器件的效率提高了75%, 达到7.0 cd/A. 相似文献