Enhanced sol–gel polymerization of organoallylsilanes by solvent effect

Abstract

We investigated solvent effects on the acid-catalyzed deallylation of organoallylsilane precursors to identify mild sol–gel polymerization conditions. Organoallylsilanes are expected to be alternative precursors for preparation of functionalized organosilica hybrids but they undergo sol–gel polymerization with difficulty due to their low reactivity towards hydrolysis. Sol–gel polymerization of model organoallylsilane precursors was conducted in various organic solvents and deallylation was monitored by 1H NMR spectroscopy. The nature of the solvent was found to strongly influence the deallylation rate and a significant correlation was observed between reaction rate and solvent basicity, which suggests that proton activity is a key factor in enhancing the reaction rate. In particular, acetonitrile was found to most effectively enhance the rate, and it accelerated the formation of a spirobifluorene-bridged organosilica hybrid film from its allylsilane precursor under a mild acidic condition. This key finding can be generally utilized for the preparation of organoallylsilane-derived highly functionalized organosilica hybrids.