Silica dissolution as a route to octaanionic silsesquioxanes

The octaanion, [OSiO1.5]88− (OA) is a low cost, discrete nano silica particle that can be made directly from high surface area, amorphous silica reacted with Me4NOH in water alcohol mixtures. It would be ideal if Me4NOH could be formed in situ from, for example, Me4NCl and NaOH, as long known in the literature. This process would reduce costs and enable recycling of Me4NCl produced in the functionalization of OA with chlorosilanes, RMe2SiCl, to form [RMe2SiOSiO1.5]8 organic/inorganic hybrid nanobuilding blocks. Kinetic studies were conducted to assess base-promoted dissolution of fumed silica (25 m2/g) as a function of concentrations, times, etc., to form the octaanion [OSiO1.5]88− using Me4NOH, NaOH and mixtures of NaOH/Me4NCl. Surprisingly, we find that small amounts of Me4NCl greatly inhibit the dissolution reaction for reasons that are as yet unknown. Copyright  2006 John Wiley & Sons, Ltd.