A Raman study of the effect of formamide on the tetramethoxysilane sol–gel process

Raman spectroscopy has been employed to investigate the sol–gel process that uses systems of tetramethoxysilane solutions added with various concentrations of formamide at ambient temperature and pressure. Although the gelation time will be shortened by formamide, both hydrolysis and the silicate network-growing rate are hindered in the sols made with formamide. It was observed that, in addition to the effect of hindering the volume shrinkage, the local concentration of formamide is increased due to the trapping of the internal silicate networks. The C–O vibrational mode of methanol was also chosen as a probe to monitor the sol–gel processes up to a period of a few hundred times the gelation time.