Interplay between Stereocomplexation and MicrophaseSeparation in PS‑ b ‑PLLA‑ b ‑PDLA Triblock Copolymers

Polymers with different tacticities or chiralities can self-assemble into stereocomplex structure (sc-structure) which may further self-assemble into sc-crystals. This stereocomplexation behavior has a great potential in enhancing the crystallization and mechanical properties of polymers. However, less is known about its interplay with microphase separation (MS) in controlling the microscopic structures of block copolymers. In this work, we have designed and synthesized two series of PS-b-PDLA-b-PLLA (PS-b-PLLA-b-PDLA) triblock copolymers. By introducing a PDLA block into a strong segregation PS-b-PLLA system, we were able to explore the interplay between stereocomplexation, crystallization, and MS. The first series of triblock polymers have a fixed total molecular weight and a PLA weight fraction about 0.3, corresponding to a cylinder MS structure. By increasing the relative PDLA:PLLA composition approaching to unity within the PLA block, we found that the long period, L0, of the MS structure decreases d...