The correlation between crystallization kinetics and polymorphism behavior in the nanocomposite of poly(vinylidene fluoride) and quaternary phosphonium salts

Dominant electroactive phases (beta- and gamma-phase) are induced in poly(vinylidene fluoride) (PVDF) by simply melt-blending with a small amount of quaternary phosphonium salts (QPS), required no organic treatment for regularly used inorganic nanofillers. Two kinds of QPS with similar structure are selected to investigate the correlation between crystallization kinetics from melt and electroactive phase formation of PVDF. What is more, nearly 100% electroactive phase is achieved. Tetraphenylphosphonium bromide (TPPB) can effectively increase the crystallization rate of PVDF and initiate the PVDF crystallize into gamma-phase directly from the melt. Smaller amount of tetraphenylphosphonium chloride (TPPC) added into PVDF matrix achieves an abrupt increasing of the crystallization rate and cause the PVDF trend to crystallize into beta-phase. Moreover, the crystallization regime II disappears or moves to higher temperature where the crystal growth rate is controlled by segmental diffusion rate together with the secondary nucleation rate. These results can be attributed to a stronger interaction between the TPPC nanoparticles and PVDF chain segments than TPPB. The inductive mechanism of TPPB and TPPC on PVDF polymorphism behavior is also researched. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim