Multicolor electrochromism of low-bandgap copolymers based on pyrrole and 3,4-ethylenedioxythiophene: Fine-tuning colors through feed ratio

Abstract

The copolymerization of pyrrole with 3,4-ethylenedioxythiophene (EDOT) is successfully achieved in boron trifluoride diethyl etherate via direct anodic oxidation of the monomer mixtures on indium-tin oxide working electrodes. The resultant copolymers are characterized by electrochemical methods, FT-IR, XPS, SEM, and spectroelectrochemical analysis. The copolymer films present excellent electrochromic properties especially the multicolor electrochromism which can be tuned through the feed ratio of pyrrole and EDOT. The neutral copolymer films exhibit blue-shift with the increasing feed ratio of pyrrole and EDOT, and the calculated band gaps of the copolymers are as low as that of PEDOT film. Furthermore, the electrochemical and optical stability has been improved by the incorporation of EDOT units into the polymer chains. The copolymer prepared with the changing feed ratio of pyrrole and EDOT at 1/4 retains 71% of its original electroactivity after 500 cycles and 72% of its optical contrast after 500 steps. Copyright © 2012 Wiley Periodicals, Inc.