Low temperature wurtz-type polymerization of substituted dichlorosilanes

Abstract

We have studied the heterogeneous Wurtz-type polymerization of a number of substituted dichlorosilanes at low temperatures as a function of solvent, metal reductant, reaction temperature, reagent stoichiometry, and additives. At 65°C, aryl dichlorosilanes rapidly produce polymer while dialkyl substituted monomers do not in the absence of additives. While the rate of polymerization of the former is relatively insensitive to steric effects, it is greatly reduced by the presence of electron donating substituents. Reaction temperature is an important variable with higher temperatures producing lower yields of multimodal products. At 65°C substituted dichlorosilanes produce high molecular weight products at low monomer conversions independent of reagent stoichiometry in a manner more consistent with a chain growth process. Polymerization in the presence of potential hydrogen donating solvents and additives produced no evidence for hydrogen atom chain transfer which would be expected if trappable silyl radicals are intermediates. The evidence is more consistent with silyl anions rather than silyl radicals as the propagating species in the heterogeneous polymerization. © 1993, The Society of Polymer Science, Japan. All rights reserved.