The widely used Flory-Huggins theory of polymer solution thermodynamics was presented in the literature in 1942 [1, 2]. It is based upon the quasilattice theory of solutions [3], and leads to an equation for the free energy of mixing polymeric solute with monomeric solvent which contains a combinatorial entropy of mixing term and a regular solution theory enthalpy of mixing term. In its original form the theory contains only one adjustable parameter, characteristic of the intermolecular forces between molecules in solution. Hildebrand's solubility parameter concept [4] may be used to estimate the value of this parameter.