Multichromic polymers containing alternating bithiophenes derivatives and 4-cyanotriphenylamine unit and their application for electrochromic devices

Two structural properties related monomers 4-di(4-(2-thienyl)phenyl)aminobenzonitrile (M1) and 4-di(4-(2-(3,4-ethylenedioxythiophene))phenyl)aminobenzonitrile (M2) were successfully synthesized. Polymer P1 and P2 were characterized successfully, which were performed by cyclic voltammetry (CV), UV–vis spectroscopy and scanning electron microscopy (SEM). Spectroelectrochemical analysis revealed that the polymers film had good electrochromic properties and exhibited multi-electrochromic behavior. The polymer films showed reversible electrochemical oxidation accompanied by strong color changes with a high contrast ratio, rapid switching time and high coloration efficiency. Besides, it is interesting to find that the P1/PEDOT device and P2/PEDOT device displayed two colors (yellow, dark-blue and green, blue) belonging to primary colors, respectively. The corresponding devices based on P1 or P2 and PEDOT showed reasonable optical contrast (ΔT%), fast response time and excellent cyclic voltammetry stability; hence they are promising candidates for various applications.