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We studied the static and dynamic properties of unentangled polymer chains which have a variable strength of interaction with the confining smooth walls by means of the lattice Monte Carlo simulation based on the bond-fluctuation model, that is, investigated the wall-polymer interactions which systematically vary from attraction to repulsion. A critical value of attractive potential(εwc) is found to be -0.6kBT, and only below it can the adsorption layer of monomers be formed near the wall. At the critical point of attraction εwc, attractive interaction counterba- lances the wall-polymer excluded volume effect, which minimizes the confinement effects on both chain dimension and mobility. Influences on both chain dimension and mobility increase with the increasing of either attraction or repulsion imposed by the walls. Despite of the nature and strength of the wall-polymer interaction, with the decrease of film thickness, configurations more parallelly aligned and flattened are adopted by confined chains, and a systematic trend of deceleration is found. Variations of chain dynamics with both film thickness and wall-polymer interaction can be well explained by the corresponding changes in the confinement of the nearest-neighboring particles that surround the chains. Besides, the thickness of the interfacial layer inside polymer films, where chains adopt a flattened “pancake” shape, is about two times the bulk radius of gyration and independent of the wall-polymer interaction. 相似文献
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聚苯乙烯是一种耐辐照的通用高分子材料。用其它方法来表征其微观反应参量,辐照剂量需要很大,周期长,而用SEC-LALLS法,则仅需凝胶点前知识,相应需要时间短,有关这方面的研究工作还未见文献详细报导。 相似文献
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高分子膜湿度传感器的制备 总被引:1,自引:0,他引:1
近年来对高分子电解质湿敏材料的研制十分活跃,本文报道以聚γ-氨丙基三乙氧基硅烷季铵化合物的湿敏材料及其元件性能。 试剂 γ-氨丙基三乙氧基硅烷(盖县化工厂),使用前蒸馏,折光指数n_D~(20)为1.4190;碘甲烷、十六烷基三甲基溴化铵、甲苯、无水乙醇皆为分析纯。 相似文献
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Ping Song Guangyi Chen Zhiyong Wei Wanxi Zhang Jicai Liang 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1507-1514
The polymorphous crystallization and multiple melting behavior of poly(l-lactic acid) (PLLA) with an optical purity of 92 % were investigated after isothermally crystallized from the melt state by wide-angle X-ray diffraction and differential scanning calorimetry. Owing to the low optical purity, it was found that the disordered (α′) and ordered (α) crystalline phases of PLLA were formed in the samples crystallized at lower (<95 °C) and higher (≥95 °C) temperatures, respectively. The melting behavior of PLLA is different in three regions of crystallization temperature (T c) divided into Region I (T c < 95 °C), Region II (95 °C ≤ T c < 120 °C), and Region III (T c ≥ 120 °C). In Region I, an exothermic peak was observed between the low-temperature and high-temperature endothermic peaks, which results from the solid–solid phase transition of α′-form crystal to α one. In Region II, the double-melting peaks can be mainly ascribed to the melting–recrystallization–remelting of less stable α crystals. In Region III, the single endotherm shows that the α crystals formed at higher temperatures are stable enough and melt directly without the recrystallization process during heating. 相似文献
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Bo Jin Hal-Bon Gu Wanxi Zhang Kyung-Hee Park Guangping Sun 《Journal of Solid State Electrochemistry》2008,12(12):1549-1554
LiFePO4-C nanoparticles were synthesized by a hydrothermal method and subsequent high-energy ball-milling. Different carbon conductive
additives including nanosized acetylene black (AB) and multi-walled carbon nanotube (MWCNT) were used to enhance the electronic
conductivity of LiFePO4. The structural and morphological performance of LiFePO4-C nanoparticles was investigated by X-ray diffraction (XRD) and scanning electron microscopy. The electrochemical properties
of LiFePO4-C/Li batteries were analyzed by cyclic voltammetry and charge/discharge tests. XRD results demonstrate that LiFePO4-C nanoparticles have an orthorhombic olivine-type structure with a space group of Pnma. LiFePO4-C/Li battery with 5 wt% MWCNT displays the best electrochemical properties with a discharge capacity of 142 mAh g−1 at 0.25 C at room temperature. 相似文献
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作为一种结构参数,聚合物的分子链内旋转位阻因子可表征聚合物分子链的柔顺性,并与聚合物的许多物理性质相关联。过去实验事实表明,聚合物的辐射交联行为与其分子链柔顺性密切相关。本工作从这一结论出发,研究聚合物的分子链内旋转让阻因子(σ)与其交联参数β之间的关系,为估算聚合物σ值提供一种新方法。 相似文献