Synthesis and characterization of a new poly(methylsilane-carbosilane) for SiC precursor

Silicon carbide ceramic matrix composites (SiC-CMC) are lightweight, high-strength and high-temperature resistant thermal structural materials, which have been widely applied in high-tech fields such as aerospace. Preceramic polymers are key materials for the fabrication of such composites via the process of precursor infiltration and pyrolysis. However, the high cost of the materials has prevented their widespread use. Developing new silicon carbide ceramic precursors and reducing their preparation costs are of great significance for the advancement and application of SiC-CMC. In this work, a new silicon carbide ceramic precursor polymer, PMSCS, was synthesized via the Wurtz coupling reaction using dichloromethylmethylsilane (Cl₂CHSiMeH₂) and chloromethylmethylsilane (ClCH₂SiMeH₂) as the monomer and end-capping agent, respectively. Owing to the participation of reactive Si―H bonds in the monomer during polymerization, PMSCS is a branched polymer with a main chain consists of C―C bonds along with Si―C bonds, which exhibits good solubility and storage stability, with a ceramic yield of 74% (mass fraction) upon pyrolysis at 1000  ℃ under inert atmosphere. Compared with the most widely used Yajima method polycarbosilane, PMSCS offers a higher ceramic yield, and its synthesis is simpler, eliminating the need for a high-temperature rearrangement step. Additionally, the synthesis of PMSCS does not require expensive lithium aluminum hydride as a reducing agent, which is essential for the preparation of hyperbranched liquid polycarbosilane. Therefore, PMSCS shows promising potential as a cost effective silicon carbide ceramic precursor.