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

Abstract 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 13 C and 29 Si 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 SiC 0.70 O 1.60 , SiC 0.81 O 1.68 , and SiC 0.85 O 1.81 , respectively by EPMA, indicating that the higher unsaturation of the organic bridge led to the higher carbon content.