Synthesis and characterization of branched copolysilanes of high molecular weight with high steric hindrance

By the Wurtz reductive coupling reaction of dichloromethylphenethylsilane (D) and trichlorosilane (T), trichloromethylsilane or trichlorophenylsilane, two series of branched copolysilanes, polymethylphenethylsilene-co-methylsilynes and polymethylphenethylsilene-co-phenylsilynes, were designed and synthesized using the two procedures of “pre-polymerization” and “mixed-polymerization”. Through the characterization of gel permation chromatography, UV, and 1H-NMR, the properties of such copolysilanes were determined and discussed. It was discovered that the branching structure of the Si-backbone of copolysilanes could be controlled by the D/T ratios and the synthetic procedures of copolymerization of dichorosilane (R1R2SiCl2) to trichlorosilane (RSiCl3), and the molecular weights of the branched copolysilanes could be dramatically enhanced with the pre-polymerization procedure even if there are bulky substituents along with the Si-skeleton of the polysilanes.