Comparative study on the optical properties and stability of linear and branched polysilanes

A typical linear polysilane-poly(methylphenyl)silane and two branched polysilanes-poly(phenyl-dimethyl)silane and poly(phenyl-methylphenyl)silane were synthesized by Wurtz reductive coupling reaction. The ultraviolet (UV) absorption and photoluminescence (PL) properties of these three polysilanes were investigated. The results, that the absorption band of the two branched polysilanes tailing to visible region and the corresponding emission peak having obvious red shift compared to the linear one, indicate that branched polysilanes have lower energy band gap. Thermogravimetric analysis (TGA) demonstrates that branched polysilanes have better thermo-stability. This conclusion has been verified by the Ozawa treatment, which provides theoretical explanation on thermo-decomposition. Besides, the results of exposing to ultraviolet reveal that branched polysilanes have better ultraviolet-resistant stability.