γ-ray curing of poly(methylsilane) and poly(methylsilane-dimethylsilane) for improved ceramic yields

Poly(methylsilane) (PMS) and poly(methylsilane-dimethylsilane) copolymers (P(MS-DMS)) were synthesized by Wurtz type polycondensation reactions of methyldichlorosilane or methyldichlorosilane-dimethyldichlorosilane mixtures in toluene. The obtained polymers were sealed in Pyrex tubes under vacuum and cured with gamma-rays. Hydrogen, methane, and silane gases formed in the tubes were analyzed by GC-MS spectroscopy. IR, UV, and NMR spectra of the cured precursor suggest the formation of Si-Si cross-links with small amounts of Si-CH2-Si bridges during irradiation. Ceramic yields of the cured polymers increased as the irradiation dose increased. The pyrolysis of the precursor polymers at 1473 K yielded amorphous products with an almost stoichiometric composition. The precise C/Si ratio in the pyrolysis product depended on the starting polymer composition and the curing conditions.