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用光子相关光谱研究了四臂星形聚苯乙烯在良溶剂(四氢呋喃THF)和θ溶剂(环己烷CH)中扩散系数与溶剂的浓度和温度的依赖关系。用累积量方法分析光子相关数据给出了多分散样品的Z均扩散系数。在θ溶剂中,高于或低于θ温度时,聚合物在溶液中的分子扩散分别表现出具有在良溶剂与不良溶剂中的行为。外推浓度至零,得到无限稀时不同温度的分子扩散系数,借助Stokes-Einstein方程,给出了聚合物的流体力学半径。通过InD对I/T作图,得到了星形聚苯乙烯在THF与CH中的扩散活化能。 相似文献
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The diffusion behavior of polystyrene with narrow molecular weight distribution at 20℃ in 1, 4-dioxane was investigated by the photon correlation spectroscopy. The cumulant method was employed for the analysis of the intensity-intensity autocorrelation function measured over a wide range of the scattering vector. The diffusion coefficient D was determined as the function of concentration C in the molecular weight range of 3. 0×104-1. 20×106. In a low concentration range, D was found to be linearly dependent on C, which has been found for some other systems. The dependence of D on molecular weight at infinite dilution can be written as an empirical formula D0 = kDM-γ M, the exponent γ(0. 576 ±0. 01) is in good agreement with the result of the scaling theory. 相似文献
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用光子相关光谱测定了苯乙烯-二乙烯基苯(St-DVB)共聚超微粒在良溶剂(甲苯)与θ溶剂(环己烷)中不同温度下的分子扩散系数,与流体力学方程结合给出了该微粒在无限稀时的等效流体力学半径。微粒分子扩散与温度的关系符合Arrhenius方程。不同温度的测试结果表明,St-DVB共聚超微粒的微交联网络结构使其分子形态不易改变。在θ溶剂中,T<θ时,微粒发生聚集,表现出大分子的协同扩散;T>θ时,在较高浓度,扩散系数偏离与浓度的线性关系。流体力学作用和热运动决定了微粒分子的扩散行为。 相似文献
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大分子引发-转移-终止剂 总被引:2,自引:0,他引:2
Polystyrene and polyacrylamide prepared by BDC (benzyl diethldithiocarbamate )could be ed as macromolecular iniferter and they initated styrene or acrylamidepolymerization further. The results shoWed that chain enlargement reaction inhomogeneous systems had the character of living radical polymerization and theprodusts still contained iniferter functional groups. Polystyrene macromoleculariniferter can initiate acrylamide polymerizahon in dioxane and thepolystyrene-- block-- polyanylamide copolymers were obtained. Blocking efficiency and polymerization activity were high. 相似文献
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碳笼烯C_(60)的发现及碳笼烷C-(60)H_(60)的制备,激励人们去探索合成新的碳元素类似物和其它元素的类似物。本文利用碳和硼的笼型烷烃的化学键和几何特征,讨论碳和硼的笼状原子簇骨架的共轭关系,推导其中一些高对称化合物的原子数和几何结构,并讨论其稳定性。 1 碳和硼的笼状原子簇骨架的共轭关系 相似文献
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