Multi-color electrochromism containing green color based on electrochemically polymerized star-shaped phenyl bithiophene

A star-shaped thiophene derivative, namely PHBT, consisting of one central core of phenyl and three arms of bithiophene, was newly synthesized and characterized, in order to further investigate the relationship between the star-shaped monomer structure (central core and peripheral arm) and the polymeric electrochromic properties. Then it was further successfully prepared into the corresponding cross-linked polymer pPHBT via electrochemical polymerization. After applying positive voltage, pPHBT exhibited excellent electrochromic properties with surprising multi-color changes between three colors, orange-yellow, green and blue, and a fast color switching speed. Furthermore, electronic structure, cyclic voltammetry and electrochromic results of pPHBT can contribute much to explain the electrochromic behavior of pTPABT with the triphenylamine core and the quadruple thiophene arm. The electrochromism of pTPABT might consist of two parts derived from the oxidative states of triphenylamine and quadruple thiophene groups, respectively. This offers a new insight into the electrochromism mechanics of conjugated polymers.