Investigation Of Improvement In Electrochemical Stability Of PEDOT Based Copolymer By Star-Like Copolymerization On Carbazole-POSS Moiety

Due to their stability and reversible redox activity, PEDOT-based copolymers are extensively investigated for electrochromic applications. For that reason, different modifications have been tried on the structure of PEDOT polymer in order to control both electrochemical and optical characteristics. Copolymerization of EDOT with carbazole monomer is one of the used modifications to alter and improve electrochromic properties. Despite these modifications, the electrochemical stability of the PEDOT-based copolymers is still a debate. To this end, a star-like shape of poly (EDOT-co-OctaCBz-POSS) copolymer was electrochemically synthesized by incorporating a carbazole-substituted polyhedral oligomeric silsesquioxane (OctaCBz-POSS) nanostructure unit into the 3,4-ethylenedioxythiophene (EDOT) backbone. The electrochemical behavior of the copolymer was investigated through cyclic voltammetry (CV) and stability tests, while the spectroelectrochemical properties were characterized using UV spectroscopy, chronoabsorptometry, and CIE Lab colorimetry. The copolymer shows a band gap (~1.88 eV) and a reduced onset oxidation potential compared to PEDOT, suggesting that the electron-donating OctaCBz-POSS enhances charge injection. The electrochemical stability of the copolymer retains about 25% after 120 cycles, whereas PEDOT loses its electroactivity after 60 cycles. UV-Vis spectroscopy indicates a slight hypsochromic shift compared to PEDOT, and chronoabsorptometry demonstrates good coloration efficiency (~245 at 570 nm), and rapid switching (~1.0 s). Upon applying a potential, the copolymer exhibited a wide range of colors, from deep purple (L* ~22, a* ~21, b* ~41) at -1.0 V to blue-gray (L* ~59, a* ~-10, b* ~-19) at 1.5 V, depending on the applied voltage.