Synthesis, characterization, and thermoelectric properties of a conducting copolymer of 1,12-bis(carbazolyl)dodecane and thieno[3,2-b]thiophene

Poly(1,12-bis(carbazolyl)dodecane-co-thieno3,2-b]thiophene) (P(2Cz-D-co-TT)), a conducting copolymer was synthesized electrochemically by direct anodic oxidation of 1,12-bis(carbazolyl)dodecane (2Cz-D) and thieno3,2-b]thiophene (TT) in boron trifluoride diethyl ethrate containing 30% (vol) dichloromethane. As-formed copolymers exhibited high redox activity and reversibility and good conductive properties. The emitting property of as-formed copolymer was different from those of respective homopolymers, and could be tuned by changing the initiate monomer feed ratios. Thermoelectric investigations revealed that the electrical conductivities of as-obtained copolymer films were between 0.1 and 0.3 S cm⁻¹ at ambient temperature, lower than that of polythieno3,2-b]thiophene (PTT) (0.42 S cm⁻¹) but two orders of magnitude higher than that of poly(1,12-bis(carbazolyl)dodecane) (P2Cz-D) (10⁻³ S cm⁻¹). The Seebeck coefficients and the power factors of the copolymers were improved with different degrees compared with those of PTT and P2Cz-D. As expected, the thermoelectric performance of PTT and P2Cz-D were both improved through copolymerization, which may be beneficial to the exploration and investigation of novel organic thermoelectric materials.