INTERFACE STABILIZATION AND MICELLE FORMATION IN BLENDS WITH A BLOCK COPOLYMER

The phase separation behavior of ternary blends of two homopolymers, PMMA and PS, and a block copolymer of styrene and methylmethacrylate, P(S-b-MMA), was studied. The homopolymers were of equal chain length and were kept at equal amounts. Two copolymers were used with blocks of equal length, which exceeded or equaled that of the homopolymer chains. Varied was the copolymer content f. Films were cast from toluene, which is a nonselective solvent. The morphologies of the cast films were compared with the structure of the critical fluctuations in solution, which were calculated in mean field approximation. The axis of blend compositions f can be divided into parts of dominating macrophase and microphase separation. Above a transition concentration fo, all copolymer chains are found in phase interfaces. Below fo, part of them form micelles within the homopolymer phases. © 1990 Steinkopff.