Non-equilibrium Thermodynamic Model for the Estimation of the Soret Coefficient in Dilute Polymer Solutions

In the present work a theoretical model based on linear non-equilibrium thermodynamics and the concept of Eyring's activation energy of viscous flow is developed to estimate the Soret coefficient in dilute polymer solutions. The model is capable of predicting a sign change in the Soret coefficient, when the polymer molecular weight changes. The key part of the model is the way that the net heat of transport of the polymer molecules is simulated. Employing the Mark-Houwink equation, which correlates the polymer solution intrinsic viscosity with its molecular weight, the net heat of transport of the polymer is correlated with the activation energy of viscous flow of the polymer's monomer in the liquid state, the Mark-Houwink solution parameter, and the polymer molecular weight. The model is evaluated against the experimental data, where qualitative and in some cases quantitative agreement is found.