Zhang Meimei, Müller-Plathe Florian
Physical Chemistry, Technische Universität Darmstadt, D-64287 Darmstadt, Germany.
J Chem Phys. 2006 Sep 28;125(12):124903. doi: 10.1063/1.2356469.
Thermal diffusion in dilute polymer solutions is studied by reverse nonequilibrium molecular dynamics. The polymers are represented by a generic bead-spring model. The influence of the solvent quality on the Soret coefficient is investigated. At constant temperature and monomer fraction, a better solvent quality causes a higher affinity for the polymer to the cold region. This may even go to thermal-diffusion-induced phase separation. The sign of the Soret coefficient changes in a symmetric nonideal binary Lennard-Jones solution when the solvent quality switches from good to poor. The known independence of the thermal diffusion coefficients of the molecular weight is reproduced for three groups of polymers with different chain stiffnesses. The thermal diffusion coefficients reach constant values at chain lengths of around two to three times the persistence length. Moreover, rigid polymers have higher Soret coefficients and thermal diffusion coefficients than more flexible polymers.
通过反向非平衡分子动力学研究了稀聚合物溶液中的热扩散。聚合物由通用的珠簧模型表示。研究了溶剂质量对索雷特系数的影响。在恒定温度和单体分数下，溶剂质量越好，聚合物对冷区域的亲和力越高。这甚至可能导致热扩散诱导的相分离。当溶剂质量从好变差时，对称非理想二元 Lennard-Jones 溶液中索雷特系数的符号会发生变化。对于三组具有不同链刚度的聚合物，重现了热扩散系数与分子量无关的已知特性。热扩散系数在链长约为持久长度的两到三倍时达到恒定值。此外，刚性聚合物比柔性聚合物具有更高的索雷特系数和热扩散系数。
