An ambipolar electrochromic polymer based on carbazole and naphthalene bisimide: Synthesis and electro-optical properties

In this study, an ambipolar polymeric electrochromic material bearing naphthalene bisimide and carbazole derivative (NBIC) was synthesized and then directly polymerized onto ITO/glass surface via potentiodynamic electrochemical process. The electrochemical and optical properties revealed that the charge transfer from carbazole-donor to naphthalene bisimide-acceptor at the ground state. When the spectro-electrochemical properties of the polymer film were investigated, various colors were obtained due to ambipolar redox behavior at both cathodic and anodic regime. In the positive regime, the polymer film exhibits two reversible oxidation waves and transparent color of the film turned into green and then turquoise resulting from the association of polaronic and bipolaronic species from carbazolylium cation radicals. Besides, in the negative regime, transparent color of the film converted to reddish brown attributed to two electron stepwise reduction of the naphthalene bisimide moiety. Finally, the polymeric electrochrome exhibits multi-electrochromic behavior, reasonable redox stability, coloration efficiency and reasonable response time.