Nanophase morphology and crystallization in poly(vinylidene fluoride)/polydimethylsiloxane-block-poly(methyl methacrylate)-block-polystyrene blends

An approach to achieve confined crystallization of ferroelectric semicrystalline poly(vinylidene fluoride) (PVDF) was investigated. A novel polydimethylsiloxane-block-poly(methyl methacrylate)-block-polystyrene (PDMS-b-PMMA-b-PS) triblock copolymer was synthesized by the atom-transfer radical polymerization method and blended with PVDF. Miscibility, crystallization and morphology of the PVDF/PDMS-b-PMMA-b-PS blends were studied within the whole range of concentration. In this A-b-B-b-C/D type of triblock copolymer/homopolymer system, crystallizable PVDF (D) and PMMA (B) middle block are miscible because of specific intermolecular interactions while A block (PDMS) and C block (PS) are immiscible with PVDF. Nanostructured morphology is formed via self-assembly, displaying a variety of phase structures and semicrystalline morphologies. Crystallization at 145 degrees C reveals that both alpha and beta crystalline phases of PVDF are present in PVDF/PDMS-b-PMMA-b-PS blends. Incorporation of the triblock copolymer decreases the degree of crystallization and enhances the proportion of beta to alpha phase of semicrystalline PVDF. Introduction of PDMS-b-PMMA-b-PS triblock copolymer to PVDF makes the crystalline structures compact and confines the crystal size. Moreover, small-angle X-ray scattering results indicate that the immiscible PDMS as a soft block and PS as a hard block are localized in PVDF crystalline structures. (c) 2019 Society of Chemical Industry