Interconnected porous BT-VTS/PVDF-HFP nanocomposites with enhanced electroactive β-phase and crystallinity fabricated via thermally induced phase separation

Porous poly(vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP, matrix nanocomposites reinforced with 25 wt% BaTiO3 nanoparticles, functionalized with vinyltrimethoxysilane (VTS) as a silane coupling agent, are produced by mixed solvent phase separation (MSPS) using dual solvents (DMF/Acetone) at different ratios (100:0-25:75) and thermally induced phase separation (TIPS) using varied solvent evaporation temperatures (90 degrees C-25 degrees C). The microstructure of porous 25% BT-VTS/PVDF-HFP nanocomposites is investigated in comparison with porous neat PVDF-HFP thin films produced by the same methods. Furthermore, the effect of temperature on pore formation, solvent evaporation, phase evolution, and crystallization behavior of the nanocomposites produced by TIPS is explored. The results exhibit that MSPS yields a porous surface for neat thin films but no for nanocomposites. In TIPS, the lower temperatures lead to macropore formation on the surface of nanocomposites. An interconnected (sponge-like hierarchically) porous microstructure is set at 25 degrees C by liquid-liquid phase separation in both neat thin films and nanocomposites. The decreasing temperature from 90 to 25 degrees C declines solvent evaporation rate and raises the porosity of nanocomposites from 17 to 54%. Furthermore, it increases their electroactive beta-phase fraction and crystallinity from 45 to 73% and from 14 to 25%, respectively. Therefore, interconnected porous 25% BT-VTS/PVDF-HFP nanocomposites stand out due to their superior properties, and they are considered potential candidates for lithium-ion battery separators, biomedical applications, piezocatalytic membranes, and piezoelectric energy harvesting.