PHASE-EQUILIBRIA IN POLYMER-PARTICLES-SOL VENT SYSTEMS - INCOMPATIBILITY AND COMPLEX-FORMATION

Two mechanisms of the separation of the polymer-small particles-solven t systems into two macroscopic phases are considered theoretically. On e of these mechanisms is due to incompatibility and the other one is d ue to complexation. These two regimes are characterized by different c omponent distributions between the phases; transition from one mechani sm to the other occurs in a narrow range of external conditions. Phase compositions in the system of poly(N-vinylpyrrolidone) and sol of pol ysilicic acid were studied experimentally. It was shown that the regim e of complexation is implemented in acidic media, whereas in neutral a nd alkaline media the regime of incompatibility is observed; moreover, this transition occurs in a narrow pH range (from pH 6 to 7).