Neutral Black Color Showing Electrochromic Copolymer based on Dithienopyrroles and Benzothiadiazole Derivatives

A novel monomer of 4-(4H-dithieno[3,2-b:2 ',3 '-d]pyrrol-4-yl)-N,N-dimethylaniline (TPDA) based on pyrrole and thiophene units was designed and synthesized, with the homopolymer and copolymer with 4,7-di(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)benzo[1,2,5]thiadiazole (BDT) prepared by an electrochemical method. Both polymers exhibited good electrochemical properties. Spectroelectrochemical features were investigated using an electrochemical station and UV-vis spectrophotometer. PTPDA film showed orange color in the neutral state and blue color for the oxidation state while PBDT film exhibits a neutral green color and light blue for the oxidation state. The copolymer film can cover the entire visible region due to its possessing the absorption features of both PTPDA and PBDT films, which exhibits black color in the neutral state (0 V) and blue color in the oxidation state (1.0 V). In addition, both the homopolymer and copolymer exhibit good electrochemical stability and coloration efficiency. These electrochromic properties make them as potential candidates for applications.