Truxene-based multisite-polymerized electrochromic polymers: Multicolor variation, excellent cycling stability, and flexible devices

In this study, two solution-processable electrochromic polymers (ECPs), PTr-EDOT and PTr-ProDOT, were synthesized via multi-site direct arylation polymerization (DArP) based on truxene and EDOT derivatives. Comprehensive characterization of their optical, electrochemical, morphological, and electrochromic properties was conducted. PTr-EDOT exhibited stable dynamic multicolor switching among yellow, green, blue, and violet, maintaining 90 % of its optical contrast after 100 cycles. In contrast, PTr-ProDOT, modified with alkoxy side chains, showed enhanced solubility, a reduced bandgap (1.36 eV), and a low onset oxidation potential (0.16 V). Its porous film morphology enabled rapid redox switching (1.9 s/1.0 s) with a high optical contrast of 29 % and excellent cycling stability (100 % retention after 100 cycles). These results demonstrate a viable design strategy for high-performance ECPs by combining a conjugated planar core with side-chain engineering to balance solubility, charge transport, and ion mobility. This work provides a promising framework for developing multicolor, low-energy, and durable electrochromic materials for advanced optoelectronic applications.