Preparation of UV curing crosslinked polyviologen film and its photochromic and electrochromic performances

Polyether urethane diacrylate matrix (PEUDA) and acrylate-functional viologen (ACV2+) were successfully synthesized and characterized in detail by FTIR and 1H NMR spectra, respectively. Subsequently, they were used to prepare UV curing crosslinked polyviologen film in combination with 2-hydroxyethyl methacrylate (HEMA), trimethylolpropane ethoxylate triacrylate (TMPTA) and diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO). UV curing approach confined the polyviologen film on ITO electrode, which imparted the film excellent adhesion ability to ITO glass, good solvent resistance, excellent chemical stability, excellent optical and electrochemical properties. The crosslinked PACV2+ film exhibited excellent photochromic and electrochromic performances. After UV illumination for 60 s, the crosslinked PACV2+ film can swiftly change its color from pale yellow to deep blue, while the optical transmission of crosslinked PACV2+ film at 610 nm did not change significantly and still retained about 63.6% after 30 cycles. Simultaneously, the cyclic voltammetry experiment showed the PACV2+ film can undergo repeatable electrochemical redox reactions with good reversibility beyond the 10th scan. Furthermore, the electrochromic device composed of the PACV2+ film and gel electrolyte film can undergo reversible color change in response to the external voltages of −2.0 V and 2.0 V, respectively, while the contrast of EC device at 610 nm did not change significantly and still retained about 39.5% after 10 cycles. This UV curing approach to preparing viologen-functional film offers a method to preparing large-scale photo- and electrochromic device, which is relatively simple, high productivity, energy saving, and environmental protection.