Photochromic and electrochromic performances of new types of donor/acceptor systems based on crosslinked polyviologen film and electron donors

Abstract

Viologen-functionalized copolymer COPV2+ was synthesized by copolymer graft-modified, which was crosslinked by NH3·H2O gas-fumigated at 25°C for 4h due to the condensation of the siloxanes of COPV2+ film. Simultaneously, different donor/acceptor systems had been prepared based on crosslinked polyviologen film (COPV2+) and N,N,N′,N′-tetramethyl-1,4-phenylenediamine (TMPD) or hydroxyethylferrocene (HEFc) in order to shorten the response times and improve contrast ratios in response to external photo- and potential stimuli. The evolution of structures from COPO to COPV2+ is carefully characterized. The COPV2+/TMPD and COPV2+/HEFc films exhibited both photochromic and electrochromic performances. After UV irradiations, COPV2+/TMPD and COPV2+/HEFc films changed their colors from colorless to deep blue, while optical transmissions at 610nm decreased about 64% and 75%, respectively. When removing out from UV irradiation, the colored COPV2+/TMPD and COPV2+/HEFc films faded to the original colors within about 60min. When COPV2+/TMPD and COPV2+/HEFc films were biased with negative voltage of −2.5V, they changed their colors from colorless to deep blue in 4s and 3s, while the optical transmissions at 556nm decreased about 81% and 75%, respectively. When electric impulse was switched off, the colored COPV2+/TMPD and COPV2+/HEFc films faded to the original colors within about 7s and 6s, respectively.