Synthesis And Characterization Of Low Band Gap Conjugated Polymers Based Phenothiazine Derivatives

In accordance with polymer band gap engineering, two series of conjugated polymers with different chemical structure in the main chain were designed and synthesized by Knoevenagel and Yamamoto reactions respectively. Chemical structure of monomers and polymers were confirmed by nuclear magnetic resonance ('H-NMR), infrared spectroscopy(IR). Molecular weight, thermal stability and optical absorption properties of the polymers were characterized by gel permeation chromatography (GPC), thermogravimetric analysis (TG) and ultraviolet-visible spectroscopy (UV-vis).Firstly, three conjugated polymers(PPCN, PBPCN and PP-PBP-CN) with low band gap were synthesized through Knoevenagel reaction according to the alternating donor-acceptor strategy. The incorporation of alkyloxybenzene group into the compound phenothiazine could not only improve the optical absorption properties but also strengthen the thermal stability. UV-vis results indicated that polymer PBPCN exhibited the best optical absorption properties, the maximum absorption wavelength reached 601nm, which was regarded as good candidates for photovoltaic materials due to its low band gap.Then, another three conjugated polymers(PBP, PBPS and PBPSe) were synthesized through Yamamoto reaction. The optical absorption properties of polymers (PBPS and PBPSe) were better than those of polymer PBP, and their edge absorption wavelength reached 750nm and 800nm respectively. But they still could not match the terrestrial solar spectrum well, their maximum absorption wavelength just covered the purple light region. It was due to the fact that their molecular weight were low and the donor and acceptor arranged randomly in the main chain.