Synthesis And Mechanism Of Self-doped Polythiophene Block Copolymers

Thiophene derivative polymers have became one of the important conductive polymer materials in photovoltaic devices for their better optical and electrical properties. It is an effective way to improve photoclectric properties by chemical bonding functional groups (e.g.-SO3-) on the molecular chain. Here, we developed a trategy for producing a conjugated polymer with both higher conductivity and doped stability during repeated electric cycles.2,5-dibromo-3-hexylthiophene and sodium styrene sulfonate were used as monomers, some different proportions of self-doping segments of 3-hexylthiophene-b-Sodium styrenesulfonate block copolymer (P3HT-b-PSSNa) were obtained by combinating solution copolymerization and Grignard metathesis (GRIM) reaction. The copolymers have regular structures and narrow molecular weight distributions. In comparison with that of v-P3HT, they have boarder UV absorption, higher conductivity, narrower band gap and amphiphilic solubility. The UV transmittance of the films was increased with increasing the proportion of PSSNa segments. By the comparison test of three block copolymers, the best block ratio is P3HT:PSSNa=1:0.4. Which have the best the photophysical and electrochemical properties, the UV maximum absorption peak had a red shift of ca. 20nm and 65nm in chloroform solution and in the form of film, respectively. The band gap (Eg=1.61 eV) is the narrowest and the conductivity is the highest.Using 3,4-ethylenedioxidethiophene and sodium styrene sulfonate were used as monomers, some different proportions of block segments of 3, 4-ethylenedioxidethiophene-b-Sodium styrenesulfonate block copolymer (PEDOT-b-PSSNa) were synthesized by combinating solution copolymerization and ’one-pot’Grignard metathesis (GRIM) method. The copolymers have controllable molecular weight, narrow molecular weight distribution and regular structure.In comparison with that of PEDOT, they have boarder UV absorption, higher conductivity, narrower band gap and amphiphilic solubility. The UV transmittance of the films was increased with increasing the proportion of PSSNa segments. By the comparison test of three block copolymers, the best block ratio is PEDOT:PSSNa=1 0.25. Which have the best the photophysical and electrochemical properties, the UV maximum absorption peak had a red shift of 31nm in chloroform solution. The UV absorption peak of the film was red shifted from 520nm to 560nm after annealed. The band gap (Eg=1.45 eV) is the narrowest and the conductivity is the highest(2.26× 10-1 S·cm-1).