Electrochromic Properties of a Copolymer of 1-4-Di[2,5-di(2-thieny1)-1H-1-pyrroly1]benzene with EDOT

Homopolymer of 1-4-di[2,5-di(2-thienyl)- 1H-1-pyrroly1]benzene and its copolymer with 3,4-ethylenedioxythiophene (EDOT) were electrochemically synthesized and characterized. Resulting homopolymer and copolymer films have distinct electrochromic properties. At the neutral state, homopolymer has lambda(max) due to the pi-pi* transition as 410 nm and E-g was calculated as 2.03 eV. The resultant copolymer revealed multichromism through the entire visible region, displaying red-violet, brownish yellow green, and blue colors with the variation of the applied potential. For the copolymer, lambda(max) and E-g were found to be 450 nm and 1.66 eV, respectively. Double potential step chronoamperometry experiment shows that homopolymer and copolymer films have good stability, fast switching times, and high optical contrast in NIR region as 41 and 30%, respectively. Copolymerization with EDOT not only decreases the band gap, E-g, but also enhances the electrochromic properties. Hence, electrochemical copolymerization is considered to be a powerful tool to improve the electrochromic properties of N-substituted 2,5-di(2-thienylpyrrole) derivatives. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1082-1087, 2009