Effect of Dithienopyrrole Unit on Electrochromic and Optical Properties of Benzotriazole-Based Conjugated Polymers

A series of benzotriazole (BTz)- and dithienopyrrole (DTP)-based three polymers; poly[2-(2-dodecyl-2H-benzo[d][1,2,3]triazol-4-yl)-4-hexyl-4H-dithieno[3,2-b:2',3'-d]pyrrole] (P1), poly[2- (5-(2-dodecyl-7-(thiophen-2-yl)-2H-benzo[d][1,2,3]triazol-4-yl)thiophen-2-yl)-4-hexyl-4H-dithieno[3,2-b:2',3'-d]pyrrole] (P2), and poly[2-(5-(2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzo[d][1,2,3]triazol-4-yl)-3-hexylthiophen-2-yl)-4-hexyl-4H-dithieno[3,2-b:2',3'-d]pyrrole] (P3) was synthesized via Stille coupling. To investigate the effect of the p-bridges on the electrochromic properties of BTz-based polymers, thiophene and 3- hexylthiophene was incorporated between BTz and DTP moiety. Different p-bridges affected the HOMO and LUMO energy levels, coloration efficiency, switching time, and optical contrast.