Crystallization of poly(vinylidene fluoride)-SiO sub(2) hybrid composites prepared by a Sol-gel process

Organic-inorganic hybrid composites consisting of poly(vinylidene fluoride) (PVDF) and SiO sub(2) were prepared through a sol-gel process and the crystallization behavior of PVDF in the presence of SiO sub(2) networks was investigated by spectroscopic, thermal and x-ray diffraction measurements. The hybrid composites obtained were relatively transparent, and brittleness increased with increasing content of tetraethoxysilane (TEOS). It was regarded from FT-IR and DSC thermal analyses that at least a certain interaction existed between PVDF molecules and the SiO sub(2) networks. X-ray diffraction measurements showed that all of the hybrid samples had a crystal structure of PVDF gamma -phase. Fresh gel prepared from the sol-gel reaction showed a very weak x-ray diffraction peak near 2[thetas]=21 degree due to PVDF crystallization, and intensity increased gradually with time after gelation. The crystallization behavior of PVDF was strongly affected by the amount of SiO sub(2) networks. That is, SiO sub(2) content directly influenced preference and disturbance for crystallization. In polymer-rich hybrids, SiO sub(2) networks had a favorable effect on the extent of PVDF crystallization. In particular, the maximum percent crystallinity of PVDF occurred at the content of 3.7 wt% SiO sub(2) and was higher than that of pure PVDF. However, beyond about 10 wt% SiO sub(2), the crystallization of PVDF was strongly confined.