Preparation of Polysilanes in the Presence of Ultrasound

摘要

Sonochemistry is based on the implosive collapse of cavities with very high pressures and temperatures existing locally for a short time. Sonochemical reductive coupling of chlorosilanes with lithium leads to the formation of disilenes and cyclotrisilanes. We have used a similar method for the preparation of high molecular weight polysilanes. The latter materials have exciting photochemical and photophysical properties which confirmed earlier theoretical predictions concerning conjugation of the catenated silicon-silicon bonds in linear polymers. The properties of polysilanes depend on the degree of polymerization and structure-properties relationships should be established for well-defined species with controlled molecular weight and low polydispersities. Monomodal polysilanes with high molecular weights and low polydispersities were prepared by the sonochemical synthesis from dichlorosilanes and sodium at ambient temperatures. The preparation dialkylpolysilanes requires the presence of etheral solvents. Copolymers of different disubstituted dichlorosilanes and a copolymer with diphenylstannane were also synthesized. Monomodality of polymers can be ascribed to the presence of one type of growing species and low polydispersity to the selective degradation of polysilanes by ultrasound. Reprints. (AW).