We present the results of experimental study on measuring the thermodiffusion, molecular diffusion and Soret coefficients of polystyrene (4,880 g/mol) in the pure solvents toluene and cyclohexane at 298 K and atmospheric pressure. The experiments have been carried out for a wide range of concentrations, starting from the diluted state with 2 % polystyrene mass fraction (proposed in the DCMIX4 project) up to the semidilute regime of 20 % polystyrene mass fraction. In addition, we present a complete characterisation of the thermophysical properties of the analysed mixtures. Thermodiffusion, molecular diffusion and Soret coefficients of binary polymeric samples have been measured by combining the traditional thermogravitational column technique, the thermogravitational microcolumn and the optical beam deflection method. In toluene, the obtained experimental results are consistent with literature, showing that the magnitude of the mass transport thermoproperties decrease significantly with increasing polystyrene concentration, which is a first indication of an approaching glass transition in the concentrated regime. The results for thermodiffusion and molecular diffusion coefficients in cyclohexane as a function of concentration exhibit a similar trend. Nevertheless, the Soret coefficient seems to show an opposite tendency for the two solvents, increasing in magnitude for cyclohexane, at least up to the analysed polystyrene concentration.

中文翻译：

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二元聚合物混合物在甲苯和环己烷中的热扩散、扩散和Soret系数


我们介绍了在 298 K 和大气压下测量聚苯乙烯 (4,880 g/mol) 在纯溶剂甲苯和环己烷中的热扩散、分子扩散和 Soret 系数的实验研究结果。实验在各种浓度下进行，从 2% 聚苯乙烯质量分数的稀释状态（DCMIX4 项目中提出）到 20% 聚苯乙烯质量分数的半稀释状态。此外，我们还对所分析的混合物的热物理性质进行了完整的表征。将传统热重力柱技术、热重力微柱技术和光束偏转法相结合，测量了二元聚合物样品的热扩散、分子扩散和Soret系数。在甲苯中，获得的实验结果与文献一致，表明传质热性质的幅度随着聚苯乙烯浓度的增加而显着降低，这是浓态中接近玻璃化转变的第一个迹象。环己烷中的热扩散和分子扩散系数作为浓度函数的结果表现出类似的趋势。然而，两种溶剂的索雷系数似乎显示出相反的趋势，环己烷的索雷系数增加，至少达到分析的聚苯乙烯浓度。