Efficient synthesis of SiOC glasses from ethane, ethylene, and acetylene-bridged polysilsesquioxanes

Silicon oxycarbide glasses (SiOC-E1, E2, and E3) were obtained as black solids by hydrolysis/condensation polymerization (sol-gel process) of bis(triethoxysilyl)ethane (BTES-E1), -ethylene (BTES-E2), and -acetylene (BTES-E3), respectively, followed by pyrolysis of the resulting polysilsesquioxane gels (Gel-E1, E2, and E3) in a nitrogen atmosphere at 1000 °C. The pyrolytic reaction progresses were monitored by TGA, IR, and 13C and 29Si NMR spectroscopic analysis. Ceramic yields from the gels increased with the increase of the unsaturation degrees of the bridges, i.e. 87%, 90%, and 95% for gels Gel-E1, E2, and E3, respectively. Elemental compositions of the resulting glasses SiOC-E1, E2, and E3 were determined to be SiC0.70O1.60, SiC0.81O1.68, and SiC0.85O1.81, respectively by EPMA, indicating that the higher unsaturation of the organic bridge led to the higher carbon content.