Crystallization induced layer-to-layer transitions in symmetric PEO-b-PLLA block copolymer with synchrotron simultaneous SAXS/WAXS investigations

Abstract

The time dependent hierarchical structures and crystallization behaviors of synthetic crystalline–crystalline symmetric diblock copolymer poly(ethylene oxide)-b-polylactide (PEO-b-PLLA) were investigated by DSC and synchrotron simultaneous small-angle/wide-angle X-ray scattering (SAXS/WAXS)measurements with various isothermal crystallization conditions. DSC measurements indicated that both blocks can crystallize and melt independently. Synchrotron SAXS/WAXS results showed that the structures and crystallization behaviors of PLLA and PEO blocks influence each other and the crystallization of both blocks could induce microphase separation into layer-layer structures, however, the crystalline structures of both blocks are not affected. It is assumed that the final structure of the crystalline–crystalline block copolymer is determined by the crystallization behaviors of the blocks rather than the glass transition temperature of the PLLA block and the theoretical microphase structure of the block copolymers.