Synthesis of polystyrene derivative-silica hybrids via in situ thiol-ene reaction in the sol-gel process

Polystyrene derivative-silica hybrids are synthesized via an in situ thiol-ene reaction in the sol-gel process. Poly(p-(3-butenyl)styrene) (PBSt) which is a polymer having vinyl groups in its repeating units is used as an organic polymer and 3-mercaptopropyltriethoxysilane (MPTES) is used as a photo-induced crosslinking agent between the organic polymer and the silica matrix. MPTES is introduced to PBSt via a thiol-ene reaction by the UV irradiation. Simultaneously, an acid catalyzed sol-gel reaction of tetraethoxysilane (TEOS) proceeds. The obtained hybrids having the organic polymer content of 30%, 50%, and 70% are optically transparent. On the other hand, the hybrids synthesized without the UV irradiation are turbid or translucent. The SEM-EDX analyses of the transparent hybrids show the homogeneity of the polymer and the silica in the hybrids. These results indicate that forming covalent bonds between PBSt and silica matrix through MPTES by the UV-promoted thiol-ene reaction improves the homogeneity of the hybrids. The thermal analyses of the hybrids using TGA show the silica components are almost quantitatively introduced into the resulting hybrids. The DSC measurements show that the resulting hybrids have higher T-g than the original organic polymer.