Self‐Assembly of Nonfrustrated ABCBA Linear Pentablock Terpolymers

Abstract The effects of compositions, interaction parameters, and number of blocks on the self‐assembly of nonfrustrated ABCBA linear pentablock terpolymer melts are investigated and compared with the corresponding ABC linear triblock terpolymers using the self‐consistent field theory. For the case of symmetric interaction parameters ( χ AB N = χ BC N ) and majority B‐blocks, both ABC triblocks and ABCBA pentablocks can form intriguing A‐ and C‐domains embedded in the B‐matrix. While these morphologies persist in the ABC systems when the segregation strength is decreased, the A blocks tend to mix with the B blocks in the ABCBA pentablocks due to the chain topology, resulting in the formation of C‐domains embedded in the AB‐mixed matrix. Different phase behavior is observed for the case of asymmetric interaction parameters ( χ AB N < χ BC N ). Aside from the core–shell type structures, a number of morphologies arise due to the separation between C and AB‐mixed domains in ABCBA pentablock copolymers. The theoretical results not only capture the self‐assembling behavior of poly(isoprene‐ b ‐styrene‐ b ‐ethylene oxide‐ b ‐styrene‐ b ‐isoprene) pentablocks, but also provide concrete suggestions for designing diverse microstructures in the linear ABC‐type terpolymers.