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991.
992.
A responsive hydrogen-bonded cholesteric liquid crystal polymer (CLCP) film with controlled porosity was fabricated as an optical sensor to distinguish between methanol and ethanol in alcohol solutions. To facilitate responding the alcohols, porosity was generated by removing the nonreactive liquid crystal agent, and the hydrogen bridges of CLCP were broken. The sensitivities of CLCPs to ethanol and methanol were obtained by monitoring the wavelength shifts of the transmission spectrum at different alcohol concentrations and ratios of methanol/ethanol. Changes in the central wavelength of the CLCP network transmission spectrum allowed the methanol–ethanol ratio to be discriminated. A linear relationship between wavelength shift of CLCP networks and alcohol concentration was obtained experimentally, and the sensor characteristics were explored. The sensitivities of the CLCPs were 1.35 and 0.18 nm/% to ethanol and methanol, respectively. The sensing sensitivity of cholesteric networks to alcohol molecules increased as the methanol–ethanol ratio declined. Therefore, CLCP could act as a stimuli-responsive material to distinguish the concentrations of acetone and ethanol in mixed solutions. Furthermore, the impact of UV intensity for curing a CLC mixture on the sensing sensitivity to the different alcohol concentrations was also studied. The higher UV intensity could enhance the sensitivity to alcohol molecules and distinguishing ability between methanol and ethanol. 相似文献
993.
This work deals with a study of the dynamic and buckling analysis of polymer hybrid composite(PHC) beam. The beam has variable thickness and is reinforced by carbon nanotubes(CNTs) and nanoclay(NC) simultaneously. The governing equations are derived based on the first shear deformation theory(FSDT). A three-phase HalpinTsai approach is used to predict the mechanical properties of the PHC. We focus our attention on the effect of the simultaneous addition of NC and CNT on the vibration and buckling analysis of the PHC beam with variable thickness. Also a comparison study is done on the sensation of three impressive parameters including CNT, NC weight fractions, and the shape factor of fillers on the mechanical properties of PHC beams,as well as fundamental frequencies of free vibrations and critical buckling load. The results show that the increase of shape factor value, NC, and CNT weight fractions leads to considerable reinforcement in mechanical properties as well as increase of the dimensionless fundamental frequency and buckling load. The variation of CNT weight fraction on elastic modulus is more sensitive rather than shear modulus but the effect of NC weight fraction on elastic and shear moduli is fairly the same. The shape factor values more than the medium level do not affect the mechanical properties. 相似文献
994.
R. Goudarzi 《Journal of Macromolecular Science: Physics》2020,59(8):502-520
AbstractPolymer/expanded graphite (EG) nanocomposites have great importance in many industrial applications mainly due to their high electrical/thermal conductivity or flame retardancy. However, to fully employ the benefits of polymer/EG nanocomposites one must consider the high degree of porosity of EG. The high degree of porosity of EG can deteriorate the composites’ mechanical properties if the polymer chains cannot diffuse completely into the EG pores. In this article, an insight is given into the diffusion of unsaturated isophthalic polyester (UP) resin, consisting of a combination of maleic anhydride and isophthalic anhydride in the resin backbone, with two viscosities, into the pores of the EG particles of various degrees of porosity. The diffusion experiments were carried out on compressed EG tablets with the same density but different porosity due to the different porosity of the EG particles. The results showed that the diffusion rate of the UP resin with higher viscosity slightly decreased when the EG porosity decreased but, in the opposite way, it strongly increased for the low viscosity UP resin. The EG nanocomposites samples were molded at varying pressures. The micrographs of the fractured surfaces of the EG nanocomposites showed that the EG pores were not filled with resin, thus the EG nanocomposites had residual pores. It was found that composites containing EGs with higher expansion ratio and larger particles and pores showed larger residual pores. Furthermore, the composites prepared with the more viscous UP resin showed more residual pores. By applying a pressure of 10?bar instead of 1?bar, a reduction of 7–20% in the residual pores of the nanocomposites was observed which led to improved mechanical properties by up to 20% in flexural strength for the EG with the highest expansion ratio. 相似文献
995.
Takahiro Gunji Yukinori Nagao Takahisa Misono Yoshimoto Abe 《Journal of polymer science. Part A, Polymer chemistry》1992,30(3):371-377
From polytitanosiloxanes (PTS), SiO2–TiO2 oxide fibers with fairly good tensile strength were prepared, and their mechanical and thermal properties were investigated. The precursor fibers PTS-0.5 and PTS-1.0 were obtained by dry spinning of a highly viscous PTS solution which were formed as the reaction mixture of silicic acid (SA) with bis(2,4-pentanedionato)titanium diisopropoxide (PTP) in the molar ratios (SA/PTP) of 0.5 and 1.0. The precursor fibers PTS-0.5 were too brittle to measure their tensile strength, whereas PTS-1.0 and the heat-treated fibers were found to have tensile strength of 130 (precursor), 540 (500°C), and 450 (900°C) MPa, respectively. Heat-treatment of the fibers PTS-1.0 at above 1000°C forms anatase and rutile of titanium dioxide. The crystallization is resulted from the unreacted PTP which is not incorporated into the polymer network. 相似文献
996.
Dae Hwan Kim Seokhyeon Kang Ji Hoon Hong Ahran Kim Hanseol Jeong 《Molecular Crystals and Liquid Crystals》2019,685(1):2-6
AbstractThermo-responsive polymers have attracted much attention in recent years because they can provide a variety of applications for smart devices, but the lack of sufficient mechanical properties and late response rate of the polymers limit their applications. In the current work, we fabricated polymer nanocomposites made from poly(vinyl methyl ether) and nanofillers with photothermal conversion property such as graphene oxide, antimony tin oxide nanoparticles, and silver nanoplates. The prepared nanocomposites showed rapidly reversible and reliable transparent-opaque transitions during the repeated heating and cooling processes, suggesting that they can be applied to smart window applications. 相似文献
997.
To design high efficiency polymer solar cells(PSCs), it is of great importance to develop suitable polymer donors that work well with the low bandgap acceptors, providing complementary absorption, forming interpenetrating networks in the active layers and minimizing energy loss. Recently, we developed a series of two-dimension-conjugated polymers based on bithienylbenzodithiophene-alt-benzotriazole backbone bearing different conjugated side chains, generally called J-series polymers. They are medium energy bandgap(Eg) polymers(Eg of ca. 1.80 eV)with strong absorptions in the range of 400-650 nm, and exhibit ordered crystalline structures, high hole mobilities, and more interestingly,tunable energy levels depending on the structure variations. In this feature article, we highlight our recent efforts on the design and synthesis of those J-series polymer donors, including an introduction on the polymer design strategy and emphasis on the crucial function of differential conjugated side chain. Finally, the future opportunities and challenges of the J-series polymers in PSCs are discussed. 相似文献
998.
999.
1000.
室温离子液体增塑的纳米复合聚合物电解质研究 总被引:2,自引:0,他引:2
在室温离子液体N-乙基-N'-甲基咪唑四氟硼酸盐(EMIBF4)增塑的凝胶聚合物电解质中加入氧化铝纳米粒子, 制备了一种纳米复合聚合物电解质(nanocomposite polymer electrolyte, NCPE). 通过示差扫描量热(DSC)、X射线衍射(XRD)、热重分析(TGA)、电化学阻抗谱(EIS)等手段对其进行了表征. 结果显示, 随着氧化铝纳米粒子含量的增加, NCPE的结晶度降低, 离子导电率升高. 但是, 纳米粒子的加入量过大时反而引起NCPE的离子导电率降低. 当纳米粒子填充量为w=10%时, NCPE具有最高的室温离子导电率1.25×10-3 S•cm-1. 相似文献