Direct arylation polycondensation for efficient synthesis of narrow-bandgap alternating D–A copolymers consisting of naphthalene diimide as an acceptor

A series of narrow-bandgap polymers based on an alkyl-thiophene-flanked naphthalene diimide (TNDI) were synthesized through direct arylation polycondensation. The 1H NMR spectra indicate all polymers correspond to an alternating copolymer structure with good regioregularity. Their photophysical, electrochemical, thermal and charge transport properties are characterized. Among all of the synthesized polymers, the copolymer consisting of alternating TNDI and 4,6-di-(2-thienyl)thieno[3,4-c][1,2,5]thiadiazole performs the best among the thin film transistors, with a moderate hole mobility of 4.6 × 10−3 cm2 V−1 s−1 under ambient conditions.