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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Solvent H/D isotope effects on miscibility and Theta-temperature in the polystyrene-cyclohexane system
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Solvent H/D isotope effects on miscibility and Theta-temperature in the polystyrene-cyclohexane system

机译：溶剂H / D同位素对聚苯乙烯-环己烷体系中混溶性和Theta温度的影响

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摘要

High-accuracy cloud-point temperatures for polystyrene-cyclohexane (PS-CH) and polystryrene-deuterated cyclohexane (PS-CH-d) solutions were measured over a broad range of molecular weights: 2.5 x 10(4) less than or equal to M-w less than or equal to 1.32 x 10(7). All polystyrene samples were characterized by low polydispersity indexes. Deuterium substitution in cyclohexane shifts the UCSTs to higher values and this isotope shift increases with increasing molecular weight, reaching at the limit of infinite M-w the value 4.53 K. No isotope effect on the critical concentration has been detected. Using different methods, Theta-temperatures for both PS-CH and PS-CH-d systems were determined. All approaches generate consistent results and a remarkable isotope effect on the Theta-temperature is observed. It is shown that isotopic shifts on UCST and Theta-temperature translate as a red shift of the C-H stretching frequency of cyclohexane on its transfer from a pure liquid to polymer solution at infinite dilution. The effect of pressure on the Theta-temperature has also been analyzed and it appears to mimic that of the pressure dependence of the critical temperatures of polystyrene-cyclohexane solution. It is also shown that the frequency shift of C-H vibrations changes with pressure in a similar fashion. [References: 50]
机译：在宽范围的分子量范围内测量了聚苯乙烯-环己烷（PS-CH）和聚苯乙烯氘代环己烷（PS-CH-d）溶液的高精度浊点温度：小于或等于2.5 x 10（4） Mw小于或等于1.32 x 10（7）。所有聚苯乙烯样品的特征在于低多分散指数。环己烷中的氘取代将UCSTs移至更高的值，并且该同位素的变化随分子量的增加而增加，达到无限M-w的极限值4.53K。未检测到对临界浓度的同位素影响。使用不同的方法，确定PS-CH和PS-CH-d系统的Theta温度。所有方法均产生一致的结果，并且观察到对Theta温度的显着同位素效应。结果表明，UCST和Theta温度的同位素位移转化为环己烷在无限稀释下从纯液体转移至聚合物溶液时C-H拉伸频率的红移。还分析了压力对Theta温度的影响，并且似乎模仿了聚苯乙烯-环己烷溶液的临界温度对压力的依赖性。还表明，C-H振动的频移以类似的方式随压力变化。 [参考：50]

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