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

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 surfacemodified 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 F-19 indicated a grafting of 39-50 units of VDF. X-ray diffraction measurements together with FTIR measurements revealed that PVDF was present in the alpha 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 degrees C for neat PVDF to 173 degrees C for PVDF-g-BaTiO3 (20 wt%) and decreased the crystallinity of PVDF from 47% to 21%.