V. Gualandris et al., NMR studies on hydrolysis and condensation reactions of alkoxysilanes containing Si-H bonds, J SOL-GEL S, 13(1-3), 1998, pp. 75-80
Hydrolysis and condensation reactions of four organically modified alkoxide
s, used for the preparation of silicon oxycarbide gel precursors, have been
followed by Si-29 NMR. Triethoxysilane (HSi(OEt)(3)) and methyldiethoxysil
ane (MeHSi(OEt)(2)) react extremely fast compared to methyltriethoxysilane
(MeSi(OEt)(3)) and tetraethoxysilane (Si(OEt)(4)). Co-hydrolysis reactions
between different pairs of precursors - MeSi(OEt)(3)/Si(OEt)(4); MeSi(OEt)(
3)/HSi(OEt)(3); MeHSi(OEt)(2)/Si(OEt)(4); and MeHSi(OEt)(2)/HSi(OEt)(3) -we
re investigated by solution state Si-29 and O-17 NMR. Despite significantly
different reactivities between precursors, evidence for co-condensation re
actions has been found for each system. Finally, two-dimensional Si-29-H-1
heteronuclear correlation MASNMR spectroscopy was used to probe the local e
nvironments of the various Si sites in the product hybrid networks.