High-contrast yellow-to-green electrochromic and electrofluochromic polyamides bearing triphenylamine fused to quinoxaline aimed for self-adaptive camouflage and explosive sensor

This work provides an effective strategy for introducing a donor-acceptor-donor (D-A-D) type structure to modulate the polymer band gap, thereby achieving a multifunctional and synergistically enhanced electrochromic device (ECD). For the construction of the polymer structure, a quinoxaline (QX) moiety was utilized as a weak electron acceptor and conjugated with two triphenylamine (TPA) donors to form a new diamine monomer. This monomer was then polycondensed with three dicarboxylic acids to obtain a series of polyamides (PAs), named TPAQ-CA, TPAQ-OA, and TPAQ-SA. TPAQ-CA exhibits green color in the oxidized state, which achieves an optical contrast ratio of 80 % in the near-infrared range with short switching times of 2.9/1.5 s and maintains 80 % of the original optical contrast ratio after 2200 cycles. Owing to the distinct electrochromism from yellow to green, a self-adaptive camouflage model has also been developed for demonstration. Meanwhile, TPAQ-CA displays photoluminescence (PL) performance and aggregation-induced emission enhancement (AIEE) in the solid state, and it is responsive to explosives and HCl gas. Overall, this work highlights the great potential of these PAs for applications in camouflage and PL detection.