A new electrochromic copolymer which switched between neutral black and oxidized transmissive

In this study, two monomers, 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dio-xin-5-yl)-2-dodecyl-2H-benzo [1,2,3]triazole (M1) and 2,3-di(5-methylfuran-2-yl)-5,8-bis(2-(3,4-ethylenedioxythiophene))quinoxaline (M2), were used for the preparation of a neutral black polymer. A black polymer P(1-co-2) was successfully achieved by the electrochemical copolymerization of the two monomers with a feed ratio of 1 : 1, and then the obtained polymer was well characterized. P(1-co-1) has a wide range of absorption in the range of 400-800 nm, which makes the polymer exhibit a deep black color in the neutral state, and a transmissive light gray color could be obtained in the oxidized state. The polymer has a low band gap of 1.20 eV. Besides, a high coloration efficiency, a fast response time, as well as high transmittance changes (more than 78%) in the near-IR region were also found with this polymer, which suggested that the polymer might be a feasible candidate for the fabrication of electrochromic devices.