Core–shell structured poly(vinylidene fluoride)-grafted-BaTiO3 nanocomposites prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization of VDF for high energy storage capacitors

Abstract

Core–shell structured poly(vinylidene fluoride)-grafted-barium titanate/(PVDF-g-BaTiO₃) nanocomposites were prepared by surface-initiated reversible addition–fragmentation chain transfer (RAFT) of VDF from the surface of functionalized BaTiO₃ nanoparticles. The ceramic fillers were first surface-modified with xanthate functions to further allow the RAFT grafting of VDF. A series of structured core shells were synthesized by tuning the feed [initiator functionalized nanoparticles]₀ : [monomer]₀ ratio, varying from 3 to 5, 10 and 20 wt%. Fourier transform infrared spectroscopy (FTIR), high resolution magic angle spinning (HRMAS) NMR and thermogravimetric analysis (TGA) confirmed the successful surface functionalization of the ceramic filler and the grafting of the PVDF shell onto the surface of the BaTiO₃ cores. Transmission electron microscopy results revealed that BaTiO₃ nanoparticles are covered by thin shells of PVDF, with thickness varying from 2.2 to 5.1 nm, forming a core–shell structure. HRMAS ¹⁹F indicated a grafting of 39–50 units of VDF. X-ray diffraction measurements together with FTIR measurements revealed that PVDF was present in the α form. Thermal properties also indicated that the addition of a small amount of the BaTiO₃ filler to the PVDF matrix increased the melting temperature from 168 °C for neat PVDF to 173 °C for PVDF-g-BaTiO₃ (20 wt%) and decreased the crystallinity of PVDF from 47% to 21%.