Formation of CH3Si8O197- cubic octameric anion in (2-hydroxyethyl)trimethylammonium silicate aqueous solutions containing hydrolysis products of methyltriethoxysilane

Abstract

CH3Si8O197-, in which a Si(O-)4 unit in the cubic octameric silicate anion (Si8O208-) is displaced by a CH3Si(O-)3 unit, has been formed in aqueous solutions of mixture of hydrolysis and polycondensation products of tetraethoxysilane and methyltriethoxysilane under the presence of (2-hydroxyethyl)trimethylammonium ions. The ammonium ions have not had any significant effects on polymerization of hydrolysis products of methyltriethoxysilane in aqueous solutions and the polymerization has taken place randomly to form a widespread distribution of the species with various structures. The hydrolysis product, however, has taken part in the formation process of the cubic octameric silicate anion with the aid of the organic ammonium cations, resulting in the formation of CH3Si8O197-.