Preparation of a Polymeric Precursor to Silicon Carbide via Ring-Opening Polymerization: Synthesis of Poly[(methylchlorosilylene)methylene] and Poly(silapropylene)

A high molecular weight linear polycarbosilane, poly[(methylchlorosilylene)methylene], [-(CH3)SiClCH2-](n), has been prepared by ring-opening polymerization of 1,3-dichloro-1,3-dimethyl-1,3-disilacyclobutane. Reduction of this polymer with LiAlH4 yields the corresponding polysilapropylene, [-(CH3)SiHCH2-](n). The structures of these polymers and their monomeric precursors have been investigated by IR and, C-13, and Si-29 NMR spectroscopy, mass spectra, and GPC. The results of these studies are consistent, in the case of the polymers, with expectations for high molecular weight linear polymers with atactic configurations. The pyrolysis of the high molecular weight poly(silapropylene) was studied by TGA and was found to give a 66% ceramic yield after thermal processing at 400 degrees C, suggesting that this polymer has potential for use as a precursor to SiC ceramics.