Synthesis and characterization of a novel kind of near-infrared electrochromic polymers containing an anthraquinone imide group and ionic moieties

A novel near-infrared (NIR) electrochromic polyelectrolyte consisting of anthraquinone imide (AQI) pendants and a poly(1-vinylimidazole bromide) main chain was synthesized via radical polymerization. Its AQI content was varied by copolymerization with 1-vinyl-3-butylimidazole bromide to improve the processability of the polymer as well as the monomer conversion. The electrochemical and electrochromic properties of both homopolymer and copolymers were investigated. All the (co)polymers exhibited two reversible redox states (radical anions and dianions). Spectroelectrochemical analysis in solution showed that the radical anions possessed intense NIR absorptions with λ_max values in the range 820 to 830 nm, while the dianions exhibited absorptions between 460 and 560 nm. The homopolymer film displayed an optical attenuation of 3 dB/µm at 810 nm with a switching time of 20 s. Such a polymer can change color in a single film device without any additional electrolytes and showed a rapid response time of 1 s at 810 nm.