Statistical thermodynamics of polymer solutions

Abstract

A free-volume, random-mixing model for polymer solutions is presented. It is a straight-forward extension of Flory's equation-of-state theory and accounts for differences in the size of core volumes of segments in pure liquids and in solution. Two binary parameters are used, one related to the interaction energies and the other to segment core volumes. The model has been tested in two different ways; in one case the ratio of the segment core-volume sizes is fixed and in the other it is considered as an adjustable parameter. The theory is tested against experimental data on heats of mixing, volumes of mixing and χ interaction parameters of four poly(dimethyl siloxane) solutions and one polyisobutylene solution with satisfactory results. The theory compares favourably with existing similar theories.