Straightforward synthesis of polycarbosilanes from chlorosilanes and chloromethanes by polycondensation using magnesium and titanium(IV) chloride

Abstract

• Straightforward synthesis of polycarbosilanes (PCS) • TiCl 4 -catalyzed polycondensation in the presence of magnesium. • Thorough analysis of polymerization mechanism. The straightforward synthesis of polycarbosilanes (PCS) was achieved via the polycondensation of chlorosilanes and chloromethanes using magnesium (Mg) and titanium(IV) tetrachloride (TiCl 4 ). In this polycondensation, TiCl 4 acts as an efficient catalyst and the combined use of Mg and TiCl 4 is necessary to produce PCS. The resulting PCS are viscous colored oils that are soluble in organic solvents. The number-average molar mass ( M n ; 1.0–1.5 kg mol −1 ) and molar-mass dispersity ( Ð M ; 1.3–1.9) values of the resulting PCS were determined by size-exclusion chromatography (SEC) using polystyrene standards. The 1 H, 13 C{ 1 H}, and 29 Si{ 1 H} NMR as well as IR spectra of the resulting PCS revealed that they consist of Si–C, Si–H, Si(H)–H, C–C, and Si–Si bonds. The structures of the resulting PCS vary depending on the structures of the monomers and their initial molar ratios. The ceramic yields from the obtained PCS (23–70%) depend on the original structures of the PCS. A plausible mechanism of this polycondensation is proposed based on the results of polycondensations and model reactions.