Formation of Si-O-N networks from silsesquiazanes

Silsesquiazanes bearing different groups [RSi(NH)_1.5] _n (R = C₁₂H₂₅, Ph, H) were hydrolyzed and the resulting products were characterized. [C₁₂H₂₅Si(NH) _1.5]_n was hydrolyzed by heating in an autoclave with water at 120 °C for 16 h. [PhSi(NH)_1.5]_n was hydrolyzed by heating with water at 50 ?C for 16 h. [HSi(NH)_1.5]_n was dispersed in water at room temperature to induce hydrolysis. In the cases of [C₁₂H₂₅Si(NH)_1.5]_n and [PhSi(NH)_1.5]_n, IR analysis showed that Si-NH-Si bonds remained and that terminal Si-NH₂ bonds in silsesquiazane were preferentially hydrolyzed to form Si-OH bonds or Si-O-Si bonds. Solid-state 29Si CP/MAS NMR analysis revealed the formation of a Si-O-N network containing various Si environments. All the Si-H and Si-N bonds in [HSi(NH) _1.5]_n, on the other hand, were converted into Si-O bonds. These results reveal that Si-O-N networks can be formed from silsesquiazanes bearing dodecyl and phenyl groups under relatively moderate conditions.