Pressure-crystallized piezoelectric structures in binary fullerene C70/poly(vinylidene fluoride) based composites

The effective fabrication of polar crystalline structures of poly (vinylidene fluoride) (PVDF), such as beta and gamma, is crucial to the development of piezoelectric polymer devices. In this study, we report the effect of pressure on binary fullerene C70/PVDF-based composite with an overall good C70 dispersion, which was prepared by an easy physical and mechanical route. The C70/PVDF composites were crystallized in a piston-cylinder high-pressure apparatus, and the polymeric crystalline structures totally with extended-chain piezoelectric beta- or gamma-form lamellae were successfully achieved in the composite samples by varying temperature, pressure, crystallization time, and composite composition. The c-axis thickness of the extended-chain beta-form lamellae of PVDF in the composites increased and decreased with the increase of the applied temperature and pressure, respectively, and it increased with the increase of crystallization time. Although C70 was found to be negative for the rapid formation of beta-form PVDF crystals, it played an important role in the growth of a beta-form PVDF nanowire with extended-chain crystalline substructures. The template-free formation of such piezoelectric nanowires was attributed to a C70-induced self-assembly of the polymer, driven by physical interactions at high pressure. The pressure-crystallized C70/PVDF composites, self-reinforced with unique one-dimensional piezoelectric structures, may diversify niche applications in advanced functional polymeric devices. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1823-1833, 2013