Thermal stability and crosslinking of hydropolysilanes for use as silicon carbide precursors

Thermal stability of [(CH3SiH)30(C6H5SiCH3)70]n a hydropolysilane copolymer, in vacuum and its crosslinking reactions with vinylic silanes as crosslinking agents was evaluated in order to obtain high yields of oxygen-free silicon carbide ceramics. It was found that the polymer was thermally stable in vacuum up to 140 °C for 20 hrs based on Fourier transform infrared spectroscopy analysis. The crosslinking reactions of the polymer occurred to various extents depending on the type of vinylic silanes used as evidenced by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, gel permeation chromatography, thermogravimetry and solubility data. The additions of vinylic silanes to Si-H in the hydropolysilane were found to obey anti-Farmer's rule, despite Farmer's addition of unsaturated hydrocarbons to Si-H.