Branched polysilanes from tetrafunctional monomers

Abstract

Tetrafunctional silicon monomers have been incorporated into soluble branched polysilanes. Tetrakis(chlorodimethylsilyl)silane has been homopolymerized to form an irregular branched polymer which may contain some spiro and some bicyclic units. This polymer shows weak absorption at ∼300 nm, the region of the linear polysilane chains. It emits broadly in the region from 400 to 500 nm. The copolymers of tetrakis(chlorodimethylsilyl)silane with dichlorodimethylsilane are also soluble and in the presence of l ge amount of the tetrakis monomer emit in the region from 400 to 500 nm. By contrast, copolymers with phenyltrichlorosilane emit strongly at 450 to 650 nm, due to the phenylsilane hyperbranched structure. Small amounts of tetrachlorosilane can be incorporated into soluble polysilanes. Incorporation of =Si=units into polymers withn-hexyl substituents is very inefficient but leads to minor changes in emission spectra. Incorporation into polymers with phenyl substituents affects luminescence and increases molecular weights and broadens polydispersities. Reaction with dimethyldichlorosilane provides soluble low molecular weight oligomers and polymers. Polymers prepared with a small proportion of tetrachlorosilane show absorption and emission typical for linear polymers. Polymers synthesized with higher proportion of tetrachlorosilanes emit broadly at 400 to 500 nm, indicating the presence of Si clusters. The silicon clusters entrapped into soluble polymers are very easily oxidized as seen by the siloxane peaks in29Si NMR spectra and they should be treated under complete exclusion of oxygen.