PHASE-EQUILIBRIA OF QUASI-BINARY SYSTEMS CONSISTING OF MULTICOMPONENT POLYMER-1 AND POLYMER-2 .3. COEXISTENCE CURVE

As an extension of the theory established previously (Brit. Polym. J., 23 (1990) 285 and 299), a method for calculating the coexistence curve (CC) was proposed for multicomponent polymer 1/multicomponent polymer 2 system. The polymer composition, molecular weight distribution existing in two liquid phases and their phase volume ratio (R) can be calculated for the systems of polymer whose molecular weight characteristics and the initial composition are known in advance. Systematic computer experiments were carried out to disclose the effect of the average degree of polymerization (DP), the DP distribution of two polymers and the initial concentration on phase diagram including CC. The polydispersity of the polymers can not be ignored in CC as in the case of the cloud point curve (CPC) and the critical solution point (CSP). In the vicinity of CPC, the two-phase volume ratio changes dramatically corresponding to a slight change in the thermodynamical interaction parameter chi(12) between polymers 1 and 2. As the initial polymer concentration approaches CSP, R approaches unity and DP distributions of polymers partitioned in two phases reduce to that of the original polymers.