Synthesis and characterization of donor–acceptor type conducting polymers containing benzotriazole acceptor and benzodithiophene donor or s-indacenodithiophene donor

Two novel electrochromic copolymers, poly(benzodithiophene-benzotriazole) (PBDBT) and poly(s-indacenodithiophene-benzotriazole) (PIDBT) were synthesized successfully through Stille coupling reactions. Both polymers were characterized by cyclic voltammetry (CV), UV-Vis spectroscopy, density functional theory (DFT), colorimetry and thermal gravimetric analysis. The band gaps of the two polymers calculated according to spectroelectrochemistry data are 1.90 eV for PBDBT and 1.93 eV for PIDBT, respectively. The PBDBT film turns rosybrown to transparent grey when it is oxidized and the PIDBT film turns pale violet-red in the neutral state to transparent light grey in the oxidized state. PBDBT has an 55.0% optical contrast at 1500 nm, PIDBT has an 60.8% optical contrast at 1560 nm, and their corresponding response times are 1.49 s and 1.85 s, respectively. In addition, the coloration efficiency of PBDBT at 1500 nm is 144.70 cm2 C−1, and the coloration efficiency of PIDBT at 1560 nm is 222.00 cm2 C−1. Both copolymers demonstrate good properties, and can be promising electrochromic materials for commercial applications.