ON PHASE-EQUILIBRIA, INTERFACIAL-TENSION AND PHASE GROWTH IN TERNARY POLYMER BLENDS

A gradient squared free energy functional of the Landau-Ginzburg type is combined with Flory-Huggins theory to calculate minimum domain size s, concentration profiles and interfacial tensions in ternary polymer blends. The dynamic equations governing spinodal decomposition are lin earized to show that the minimum size for growth is identical to the t hermodynamic minimum on phase volume. It is shown that unseparated, th ird components are enriched at the interface, reduce interfacial tensi on, increase stability and increase the minimum domain sizes. Enrichme nt of the third component at the interface causes concentrations at th e major components to lie outside their binodal limits at a distance f rom the interface. Although the effects are most pronounced when the t hird component is a compatibilizer, the general phenomena remain true even when the third component is relatively incompatible. Generalizati ons to blends of N components are presented, and a robust method for c alculating multicomponent phase diagrams is described.