Silica dissolution as a route to octaanionic silsesquioxanes

Abstract

The octaanion, [OSiO 1.5 ] 8 8− (OA) is a low cost, discrete nano silica particle that can be made directly from high surface area, amorphous silica reacted with Me 4 NOH in water alcohol mixtures. It would be ideal if Me 4 NOH could be formed in situ from, for example, Me 4 NCl and NaOH, as long known in the literature. This process would reduce costs and enable recycling of Me 4 NCl produced in the functionalization of OA with chlorosilanes, RMe 2 SiCl, to form [RMe 2 SiOSiO 1.5 ] 8 organic/inorganic hybrid nanobuilding blocks. Kinetic studies were conducted to assess base-promoted dissolution of fumed silica (25 m 2 /g) as a function of concentrations, times, etc., to form the octaanion [OSiO 1.5 ] 8 8− using Me 4 NOH, NaOH and mixtures of NaOH/Me 4 NCl. Surprisingly, we find that small amounts of Me 4 NCl greatly inhibit the dissolution reaction for reasons that are as yet unknown. Copyright © 2005 John Wiley & Sons, Ltd.