Thermodynamics of poly(dimethylsiloxane) solutions

Abstract

Improved expressions for thermodynamic excess functions for mixtures of a non-polar polymer and a solvent are presented on the basis of modification of the combining rules of mixing which were assumed by Flory in the equation-of-state theory of pure fluids and their solutions. The modified theory assumes that the number of external degrees of freedom is non-additive with respect to the segment fraction and that the sizes of the core volumes of segments in pure liquids and solution are different. This theory can reproduce the experimental results of the interaction parameter χ and the excess volume of mixing, which the Flory theory failed to reproduce. Direct comparisons of the modified combining rules with experimental results is satisfactory.