Thermal stability of SiO2-based inorganic-organic hybrid materials

The hydrolysis-polycondensation of organicallly modified Si-alkoxides leads to the obtaining of inorganic-organic hybrid materials in which the organic moieties remain as permanent groups bonded to the inorganic network. The molecular species previously determinated by GC-MS during the gelation process have been significantly different according to the type of the alkoxide used. In the present work, thermal stability of SiO2-based inorganic-organic hybrid materials starting with TEOS (tetraethoxysilan), MTEOS (triethoxymethylsilan), VTEOS (triethoxyvinylsilan) and MTMOS (trimethoxymethylsilan) was studied. The molecular structure of the gels obtained determines differences in their thermal behaviour. Gels obtained starting with MTEOS show the highest thermal stability, while gels obtained using VTEOS the lowest, among the substituted alkoxides. A particular behaviour presents the gel obtained with MTMOS that decomposes in four steps. This could be explained by the presence in the gel of some prevalent types of molecular species with different thermal stability.