Sign change of the Soret coefficient of poly(ethylene oxide) in water/ethanol mixtures observed by thermal diffusion forced Rayleigh scattering.
Sign change of the Soret coefficient of poly(ethylene oxide) in water/ethanol mixtures observed by thermal diffusion forced Rayleigh scattering.
复制标题
通过热扩散强制瑞利散射观察到水/乙醇混合物中聚环氧乙烷的索雷系数的符号变化。
DOI：
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发表时间：
2004
影响因子：
4.4
通讯作者：
J. Luettmer
中科院分区：
文献类型：
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作者：
R. Kita;S. Wiegand;J. Luettmer
用热扩散强迫瑞利散射法测定了聚环氧乙烷在水/乙醇混合溶剂中的Soret系数。发现聚合物的Soret系数S（T）随着溶剂的水含量增加而改变符号，其中符号改变在22 ℃的温度下在水质量分数为0.83时发生。对于高水浓度，聚（环氧乙烷）的S（T）值为正值，即，聚合物迁移到流体的较冷区域，这对于良溶剂中的聚合物是典型的。另一方面，对于低水含量，聚合物的Soret系数为负，即，聚合物迁移到流体的较热区域。两种不同的聚合物浓度的测量结果表明，较小的聚合物浓度的Soret系数的较大幅度。研究了富水聚合物溶液的Soret系数随温度的变化规律，发现随着温度的升高，Soret系数从负变正。热扩散实验也进行了二元混合物水/乙醇。对于二元混合物，观察到水的Soret系数在水质量分数为0.71时改变符号。这与文献中的实验结果一致。我们的研究结果表明，特定的相互作用（氢键）之间的溶剂分子和聚合物和溶剂分子发挥了重要作用，在该系统的热扩散。
Soret coefficients of the ternary system of poly(ethylene oxide) in mixed water/ethanol solvent were measured over a wide solvent composition range by means of thermal diffusion forced Rayleigh scattering. The Soret coefficient S(T) of the polymer was found to change sign as the water content of the solvent increases with the sign change taking place at a water mass fraction of 0.83 at a temperature of 22 degrees C. For high water concentrations, the value of S(T) of poly(ethylene oxide) is positive, i.e., the polymer migrates to the cooler regions of the fluid, as is typical for polymers in good solvents. For low water content, on the other hand, the Soret coefficient of the polymer is negative, i.e., the polymer migrates to the warmer regions of the fluid. Measurements for two different polymer concentrations showed a larger magnitude of the Soret coefficient for the smaller polymer concentration. The temperature dependence of the Soret coefficient was investigated for water-rich polymer solutions and revealed a sign change from negative to positive as the temperature is increased. Thermodiffusion experiments were also performed on the binary mixture water/ethanol. For the binary mixtures, the Soret coefficient of water was observed to change sign at a water mass fraction of 0.71. This is in agreement with experimental results from the literature. Our results show that specific interactions (hydrogen bonds) between solvent molecules and between polymer and solvent molecules play an important role in thermodiffusion for this system.