Synthesis of hydrocarbon-soluble, methyl-substituted highly branched polysilanes via the Wurtz-type reductive coupling of trifunctional trisilanes and their pyrolysis to silicon carbide

Abstract

A hydrocarbon-soluble, methyl-substituted highly branched polysilane was synthesized by subjecting a new type of monomer to the common Wurtz-type reductive coupling reaction conditions. For this purpose, the trichloro-substituted trisilane (ClMe₂Si)₂SiMeCl (1) was used as a monomer. Polymerization was conducted at elevated temperature using dispersed sodium in toluene. Termination was initiated after 4 h by the addition of MeMgBr and precipitation in MeOH. The branched polysilane was analyzed by GPC, NMR and IR spectroscopy after quenching with MeMgBr and additionally after precipitation in MeOH. Opto-electronic properties were tested by UV/Vis and PL spectroscopy. Thermal properties were examined via TGA and DSC. The synthesized polysilane is usable as a soluble precursor for the preparation of SiC, not least due to its high silicon content. The chemical process during pyrolysis was examined at different temperatures by means of ¹H NMR, IR and UV/Vis spectroscopy. XRPD analysis, IR spectroscopy, HR-SEM-EDS and elemental analysis confirmed the successful formation of β-SiC.