Synthesis, optical properties and stability of two σ-π conjugated polycarbosilanes with silylene-1,2-diphenyleneethylene-silylene and silylene-terephthalyidene-silylene backbones via Grignard reactions

- Two PCS products with phenyl in the backbone were synthesized via Grignard reactions.
- PCS-SDS with diphenyl possesses extended σ-π conjugation and good optical property.
- PCS-SDS indicates higher quantum yield and better thermal stabilities than PCS-STS.
- Excellent PL is attributed to combined delocalization of σ-σ* and π-π* transitions.
- PCS-SDS may be an attractive candidate for organic electroluminescent devices.

Optical properties and stability of two novel polycarbosilane (PCS) products bearing aryl groups in the main chain synthesized by Grignard reactions were studied. 4-bromostyrene, α, α'-dibromo-p-xylene and dichloromethylsilane were employed as reactants to yield σ-π conjugated PCS with silylene-1,2-diphenyleneethylene-silylene backbone (PCS-SDS) and PCS with silylene-terephthalyidene-silylene backbone (PCS-STS), respectively. Effects of oxidation cross-linking and ultraviolet (UV) radiation on the luminescence properties were examined. Photoluminescence (PL) spectra exhibit excellent blue light emission (maximum emission peaks at about 422 nm) compared to PCS and the intensity is exactly enhanced due to the insertion of phenyl into the conjugated main chains with SiC bonds and the combined delocalization of the σ-σ* transitions in Si chains and the π-π* transitions in the benzene rings. Especially, PCS-SDS with more diphenyl and CC groups possesses stronger emission intensity, higher quantum yield, better oxidation and UV resistance, and excellent thermal shock behavior below 400 °C in comparison with PCS and PCS-STS. Time-resolved PL spectra analysis also indicate that PCS-SDS can maintain longer fluorescence lifetime. These results prove PCS-SDS to be potentially applied to many fields, including but not limited to polymeric semiconducting materials, nonlinearoptics and organic electroluminescence devices.

PCS-SDS products with diphenyl and CC synthesized via Grignard reactions possess extended σ-π conjugation and exhibit strong emission intensity, high quantum yield, long fluorescence lifetime, excellent oxidation, UV and thermal shock resistance.218