Neutral-state green conjugated polymers from pyrrole bis-substituted benzothiadiazole and benzoselenadiazole for electrochromic devices

Two donor/acceptor/donor-type pyrrole-incorporated monomers, 4,7-di(1H-pyrrol-2-yl)benzo[c][1,2,5]thiadiazole (M1) and 4,7-di(1H-pyrrol-2-yl) benzo[c][1,2,5]selenadiazole (M2), were synthesized and polymerized electrochemically. The resulting polymers (P1 and P2) were investigated in terms of their electrochromic and optical properties. Spectroelectrochemistry studies revealed that both polymers show two distinct absorptions in both red and blue regions. The absorptions at around 400 and 700 nm correspond to neutral-state green polymers P1 and P2, which is a unique property for conjugated polymers. Optical band gaps were calculated as 1.12 and 1.08 eV for P1 and P2, respectively. Two pyrrole-containing donor/acceptor/donor-type conjugated polymers are synthesized. Benzothiadiazole and benzoselenadiazole units are used as the acceptor moieties in the polymer structures. The polymers display green color in their neutral states, which is significant for the completion of the RGB color space.