Microphase separation in a mixture of block copolymers in the strong segregation regime

Microphase separation in a blend of A-B and C-B block copolymers with strong A-B and C-B incompability is considered in the strong segregation regime. It is assumed that the length of the B block is always much larger than the lengths of A and C blocks, so the complex spherical micelles containing shorter A and longer C chains are formed. The inner structure of the complex A-C micelle is considered, and the distribution of volume fractions of A and C monomer units is calculated. It is shown that shorter A chains are distributed mainly in the periphery of the micelle, while C chains are coiled in the center of this micelle. Macroscopic separation in this blend is studied. It is shown that, in the mixtures with a small fraction of C-B block copolymer, a two-phase structure should be observed: one phase consists of practically pure A micelles, while the other phase the complex A-C micelles, with enriched contents of longer C chains, are formed. For chemically different A and C blocks, even slight A-C repulsion leads to phase separation between the phases with pure A and pure C micelles.