AN ORIGINAL ROUTE TO POLY[SILYLENE-CO-(2,4-DISILAPENTANE-2,4-DIYL)] OLIGOMERS, EFFICIENT PRECURSORS OF SILICON CARBIDE-BASED CERAMICS WITH VARIABLE C SI RATIOS/

Novel oligomers possessing a backbone formed of (=Si-CH2-Si=) and (-Si -)(n) units were prepared by the copolycondensation of bis(chlorosilyl )methanes and various dichlorosilanes in the presence of sodium, in re fluxing toluene. The effect of the respective molar ratios of comonome rs on the yields and the structure of the copolymers was investigated. The role of substituents on silicon atoms in the ability of these mat erials to provide convenient ceramic precursors upon pyrolysis was exa mined. When =Si-H bonds were present, thermal cross-linking was readil y performed and ceramics possessing variable C/Si ratios were prepared .