Comparative study of the sol-gel processes starting with different substituted Si-alkoxides

In the present work a comparative study of the hydrolysis-polycondensation processes of different Si-substituted alkoxides, leading to hybrid materials with covalent -Si-C- bonds, was carried out. The following alkoxides were used: tetraethoxysilane (TEOS), methyltriethoxysilane (MTEOS) and vinyltriethoxysilane (VTEOS). Using gas chromatography coupled with mass spectrometry (CG-MS), nuclear magnetic resonance (Si-29-NMR) and infrared spectrometry (IR), information about the sol-gel process in the mentioned systems were obtained. The differences in the reactivity of the studied alkoxides are connected with the steric effect of the organic substituents. The reactivity of the alkoxides in the early stages of the hydrolysis-polycondensation process increased in the order TEOS < VTEOS < MTEOS. (C) 2003 Elsevier Science B.V. All rights reserved.