Hyperbranched poly(2,5-silylthiophenes). The possibility of sigma-pi conjugation in three dimensions

New hyperbranched organosilicon polymers have been prepared from 2-bromo-5- (trimethoxysilyl)thiophene. The intermediate alkoxy-substituted hyperbranch ed polymer is functionalized with Grignard reagents in situ, leading to the isolation of a series of air- and moisture-stable polymers. The polymers c ontain alternating silylene and thiophene groups along the branches and thu s afford the possibility of sigma-pi conjugation in three dimensions. Inves tigations into the effects of this dimensionality utilize UV-visible spectr oscopy.