Expanding the Realm of Soluble Narrow Band Gap Polymers with a Benzobisthiadiazole Derivative

A donor acceptor donor based soluble and narrow band gap pi-conjugated electrochromic polymer, poly(4,8-bis(3,3-dihexyl-3,4-dihydro-2H-thieno [3,4-b] [1,4] dioxepin-5-yl)b enzo [1,2c;4,5-c']bis[1,2,5]thiadiazole) (P1), was electrochemically (P1-E) and chemically (P1-C) synthesized. Cyclic voltammetry and UV-vis-NIR absorption measurements showed that P1 has a low band gap ranging from 0.59 to 1.1 eV, depending on the band gap determination and synthesis (chemical or electrochemical) methods. P1 demonstrated an ambipolar electrochemical behavior. The color of the polymer was gray in its neutral state and switched to green (first oxidation state) and blue (second oxidation state) upon oxidation and to brown upon reduction.