Structural Change of Gels Prepared from Highly Acidic Tetramethoxysilane Solutions in the Drying Process

Abstract

Sol-gel reaction of tetramethoxysilane (TMOS) under highly acidic conditions with a limited amount of water provides highly porous monolithic silica gels composed of micrometer-sized particles^1–3). Because of the continuous large pores and particles, these gels and heated derivatives may be suitable for porous materials which can be used as filters or supports for catalysts and enzymes. For these uses, surface characteristics of the gels should be controlled. Since the amount of water for hydrolyzing TMOS in the starting solutions is limited, some of alkoxy groups may be left to be hydrolyzed at the time of gelation and water in the atmosphere may affect the nature of surfaces of the large particles of the gels during drying. In the present study, the surface properties of the gels have been investigated by BET analysis and electeon microscopic observation as a function of drying time.