Heat Evolution, Light Scattering, and Infrared Spectroscopy in the Formation of Silica Gels from Alkoxides

Calorimetry, light scattering, and infrared spectrophotometry have been used to investigate the formation of silica gels from alkoxides. The heat evolution which occurs immediately on mixing tetraethyl orthosilicate (TEOS), ethanol, and water acidified with HC1, is completed before appreciable polymerization polymerization of the hydrolysis products causes an increase in light scattering. For these solutions the hydrolysis of TEOS is separate in time from the gel-forming polymerization process.