Synthesis and properties of conjugated polycarbosilanes with 1,4- bis(thiophene or phenylene)-buta-1,3-diyne

Conjugated polycarbosilanes with diacetylene and aromatic groups of thiophene or phenylene simultaneously present in the polymer backbone such as poly[[1,4-bis(thiophenyl)buta-1,3-diyne]-alt-(dimethylsilane)], poly [[1,4- bis(thiophenyl)buta-1,3-diyne]-alt-(diphenylsilane)], poly[[1,4- bis(phenyl)buta-1,3-diyne]-alt-(dimethylsilane)], and poly[[1,4- bis(phenyl)buta-1,3-diyne]-alt-(diphenylsilane)] have been prepared. The characteristic C≡C stretching frequencies appear at 2177-2179 cm^-1 in the IR spectra of the polymers. The molecular weights of these polymers were determined by GPC. All of these materials are soluble in organic solvents such as THF and chloroform, and thermally stable up to 200 °C in general without any weight loss under nitrogen. The prepared materials in THF solvent show a maximum absorption peak in the range of 334-356 nm with a molar absorptivity of 10³-10⁵ L/(cm·mol) in the UV-visible absorption spectra. A maximum emission peak in the range of 403-550 nm is also observed in the fluorescence emission spectra. Both absorption and emission spectra strongly indicate that the obtained polycarbosilanes contain the new conjugated systems along the polymer main chain.