Preparation of sol-gel hybrid materials from γ-methacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions

Organic-inorganic hybrid materials suitable for the development of sol-gel coatings for metallic surfaces were prepared by hydrolysis and condensation of gamma-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). The hydrolysis of MAPTMS/TMOS was carried out in an ethanol/water solution. The prehydrolysis stage of MAPTMS/TMOS system was monitored by Fourier transform infrared spectroscopy (FTIR) and liquid-state Si-29 and C-13 nuclear magnetic resonance (Si-29 and C-13 NMR). FTIR analysis indicated that the hydrolysis of MAPTMS/TMOS was accomplished as far as the (SiOMe) band corresponding to unhydrolyzed silane disappeared. The concentration of the alkoxy groups and the extent of self-condensation of mono-, di-, and trisubstituted siloxanes (T species) in the sol were estimated by using liquid-state Si-29 NMR spectroscopy. The hydrolysis of the prepared sol was also evaluated by liquid-state C-13 NMR spectroscopy. The results indicated that under the adopted synthesis strategy conditions, the hydrolysis process requires 4 h to be completed.