IMPORTANCE OF CYCLIZATION DURING THE CONDENSATION OF HYDROLYZED ALKOXYSILANES

Hydrolyzed alkoxysilanes exhibit decreasing condensation reactivity as the connectivity of a reacting site increases. However, until recentl y cyclization was neglected when quantifying this effect. We apply two kinetic models, one neglecting cyclization, the other accounting for cyclization (using in part the illustrated scheme), to Si-29 NMR data of hydrolyzed alkylethoxysilanes. We show that the true negative first shell substitution effect is even more severe than previously thought when neglecting cyclization.