A polyfunctional organic-inorganic hybrid monomer, methyl-tri(phenylethynyl)silane (MTPES) Could be thermally polymerized by a free radical mechanism to a highly crosslinked structure of interest as a high temperature composite matrix resin. The Structural changes during thermal cure process were characterized by fourier transform infrared Spectrum and C-13-CP-MAS-NMR spectrum. The disappearance of secondary acetylene stretching band at 2166 cm(-1) was used successfully to monitor Cure reaction accompanied with the formation of cis-polyene structure at 1600 and 754 cm(-1). The possible cure mechanism of MTPES was also proposed. The pyrolysis Of Cured MTPES tinder a stream of argon to 1450 degrees C gave a ceramic in high yield (81%). Thermal conversion of polymer to ceramic was Studied by means of X-ray diffraction, Raman spectrum, and energy dispersive spectrometer analysis. The results showed that pyrolytic products were made up of beta-SiC, graphite, and glassy carbon. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 10-16, 2009