Synthesis and characterization of all-conjugated hard-soft-hard ABA triblock copolythiophenes

A new thiophene monomer design was demonstrated by exploiting the flexibility and bulkiness of trisiloxane units to produce “soft” polythiophene materials. In practice, the thiophene monomer having trisiloxane units could be polymerized by Kumada Catalyst-Transfer Polymerization (KCTP) to afford well-defined poly(1,1,1,3,3,5,5-heptametyl-5-(6′-(thien-3″-yl)hexyl)trisiloxane-2″,5″-diyl) (P3SiHT) with low dispersity, which was viscous material with fluidity. To the best of our knowledge, it is first time to develop “liquid” polythiophene at room temperature. In addition, we are successful in synthesizing novel all-conjugated hard-soft-hard ABA triblock copolymer, where A and B were poly(3-hexylthiophene) (P3HT) and P3SiHT, respectively, based on KCTP method and sequential monomer addition technique. The livingness of the KCTP system was confirmed by size exclusion chromatography (SEC) UV traces. The formation of phase separated P3HT and P3SiHT domains in the triblock copolymer (P3HT-b-P3SiHT-b-P3HT) was supported by differential scanning calorimetry (DSC), although the existence of miscible domains was also implied.