, Volume 30, Issue 12, pp 3130-3136

Pyrolytic conversion of methyl- and vinylsilane polymers to Si-C ceramics

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Abstract

Poly(methylsilane) and poly(vinylsilane) were synthesized using a titanocene catalyst, and their pyrolytic conversion to ceramics was followed using a combination of thermal analysis and infrared spectroscopy. The two polymers have distinctly different backbone structures, as determined by29Si NMR; methylsilane polymerizes to a polysilane, while vinylsilane polymers have a predominately polycarbosilane backbone, with some polysilane structure as well. The pyrolysis path and char yield were dependent primarily on backbone structure, with little influence of polymer molecular weight. The majority of the weight loss on conversion occurs below 650 °C, although bond rearrangement continues to 1400 °C. Poly(vinylsilane) produced a carbon-rich Si-C ceramic in which the carbon was dispersed on a sufficiently fine level to show resistance to oxidation on heating in air to 1400 °C. Copolymerization of methyl- and vinylsilane produced stoichiometric SiC; however, polymers of methylsilane were sensitive to oxygen incorporation and sometimes pyrophoric. Polymerization of vinylsilane with disilylethane permitted control of rheology and imparted thermoset behaviour.