Solution-Processable Neutral Green Electrochromic Polymer Containing Thieno[3,2-<i>b</i>]thiophene Derivative as Unconventional Donor Units

Abstract

In the quest to develop novel solution-processable neutral green electrochromic polymers, the donor–acceptor (D–A) polymer PBOTT-BTD has been synthesized through direct C–H arylation polycondensation, using 3,6-bis(hexyloxy)thieno[3,2-b]thiophene instead of conventional D units and benzo[c][1,2,5]thiadiazole as the A unit. PBOTT-BTD films obtained through spray-coating were investigated systematically; this green polymer turned blue in the oxidized state, realizing a conversion between two primary colors. PBOTT-BTD exhibited rapid response times, desirable contrasts in both the visible and near-infrared (NIR) regions, favorable efficiencies, and reasonable optical memory and stability, making it a promising candidate for use as a new green electrochromic conjugated polymer. Accordingly, PBOTT-BTD might have applicability not only as an electrochromic material but also in NIR or optical memory devices, perhaps even in supercapacitor applications; the use of thieno[3,2-b]thiophene units presenting alkoxy groups might also allow the preparation of novel D–A conjugated polymers when matched with various acceptor units.