DETERMINATION OF CHI FROM LIQUID-LIQUID PHASE DATA AND THE COMPUTATION OF PHASE-DIAGRAMS FOR QUASI-BINARY POLYMER-SOLUTIONS AND BLENDS

A generalized Flory-Huggins theory is described that permits the inves tigation of the phase behavior for quasi-binary polymer solutions or b lends in which, for blends, both components may be polydisperse. A tem perature- and concentration-dependent chi interaction parameter is use d. It is demonstrated that the chi parameter may be readily extracted from experimental phase data. This is illustrated by using a robust fi tting procedure to obtain the composition and temperature dependence o f chi for the cyclochexane/polystyrene system from experimental phase data. The result (eq 22) is in excellent agreement with previous deter minations of chi for this system, and the method employed here has sev eral advantages over other approaches. Relative merits of a number of methods are discussed. The composition- and temperature-dependent chi determined here (eq 22) is used to predict cloud-point curves for solu tions of polystyrene with various bimodal distributions in cyclohexane . These computed CPCs are found to be in quantitative agreement with e xperimental data.