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 thiophe ne 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-(dime thylsilane)], and poly[[1,4-bis(phenyl)buta-1,3-diyne ]-alt-(diphenylsilane)] have been prepared. The characteristic C drop C str etching frequencies appear at 2177-2179 cm(-1) in the IR spectra of the pol ymers. The molecular weights of these polymers were determined by GPC. All of these materials are soluble in organic solvents such as THF and chlorofo rm, and thermally stable up to 200 degrees C in general without any weight loss under nitrogen. The prepared materials in THF solvent show a maximum a bsorption peak in the range of 334-356 nm with a molar absorptivity of 10(3 )-10(5) 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 emiss ion spectra. Both absorption and emission spectra strongly indicate that th e obtained polycarbosilanes contain the new conjugated systems along the po lymer main chain.