An organic-inorganic silica precursor suitable for the sol-gel synthesis in aqueous media

Partially polycondensed γ-aminopropylsilanetriol, (APSTOL) was prepared by hydrolyzing γ-aminopropyltriethoxysilane at a hydrolysis ratio 8.0. APSTOL contains up to 52% SiO2 and can be easily dissolved in water, forming clear solutions remaining stable practically at any pH value. The thermal evolution of APSTOL when heating up to 1000°C was examined using TGA and FTIR techniques; the probable mechanism of the oxidative decomposition of organic groups, with the formation of imino- and carboxyl-containing intermediates, has been discussed. Two magnesium silicates of the enstatite and forsterite, compositions and two calcium silicates of the wollastonite and rankinite, compositions have been prepared, using corresponding acetates and APSTOL as MIIO and SiO2 precursors. The crystallization, processes in these systems were studied by TGA and XRD techniques, after heat treatments up to 1000°C. In all the systems, except rankinite, the parent silicates were found as the main crystalline phases.