Preparation and properties of poly(vinyl acetate)silica-gel hybrids obtained by sol-gel process: Effect of methyl groups in silicon alkoxide

A copolymer of vinyl acetate (VAc) and vinyl triethoxysilane (VTES) having molar ratio of 9:1 was synthesized and incorporated with silica-gel by the sol-gel process. Tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), and dimethyldiethoxysilane (DMDES) were used as silicon alkoxides. The tensile strength of copoly(VAc/VTES)/silica-gel hybrids was higher than that of PVAc/silica-gel hybrids because of strong bonding between copolymer and silica-network. The strength of the copolymer hybrids prepared from TEOS and MTES increased up to 50 MPa and 43 MPa, respectively. On the other hand, the strength of the hybrid from DMDES decreased with DMDES content. The elongation of the hybrids increased by mixing 20 wt% of MTES and DMDES. The dynamic modulus, G', of the hybrids increased when they were prepared from TEOS and MTES. DMDES having two methyl groups in the alkoxide chain, decreased the G' value of the hybrid. The tan delta peak position of the hybrids from TEOS and MTES shifted to a higher temperature range with increasing amounts of mixed silicon alkoxides, but DMDES lowered the tan delta peak temperature.