Unusual thermal diffusion in polymer solutions.
Unusual thermal diffusion in polymer solutions.
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DOI：
10.1103/physrevlett.91.245501
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发表时间：
2003-12
影响因子：
8.6
通讯作者：
B. de Gans;R. Kita;S. Wiegand;J. Luettmer-Strathmann
中科院分区：
文献类型：
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作者：
B. de Gans;R. Kita;S. Wiegand;J. Luettmer-Strathmann
用热扩散强迫瑞利散射方法研究了聚环氧乙烷（PEO）在乙醇/水混合物中的热扩散。在富含水的溶剂混合物中，发现PEO向较低温度的区域迁移。这对于聚合物溶液是典型的，并且对应于PEO的正Soret系数。然而，在具有低水含量的溶剂混合物中，发现聚合物向更高的温度迁移，对应于PEO在富含乙醇的溶液中的负Soret系数。据我们所知，这是第一次观察到的索雷特系数在溶液中的符号变化。我们还提出了一个简单的晶格模型的聚合物溶剂系统和计算Soret系数的统计力学方法。计算值与实验结果定性一致。
Thermal diffusion forced Rayleigh scattering results on thermal diffusion of poly(ethylene oxide) (PEO) in ethanol/water mixtures are presented. In water-rich solvent mixtures, PEO is found to migrate towards regions of lower temperature. This is typical for polymer solutions and corresponds to a positive Soret coefficient of PEO. In solvent mixtures with low water content, however, the polymer is found to migrate towards higher temperatures, corresponding to a negative Soret coefficient of PEO in ethanol-rich solutions. To our knowledge, this is the first observed sign change of the Soret coefficient of a polymer in solution. We also present a simple lattice model for the polymer solvent system and calculate Soret coefficients with statistical mechanics methods. The calculated values agree qualitatively with the experimental results.