Facile and economical synthesis of an electrochromic copolymer for black based on electropolymerization of thiophene and 3,4-ethylenedioxythiophene

We report the facile and economical synthesis of an electrochromic copolymer for black based on electrochemical copolymerization of thiophene and 3, 4-ethylenedioxythiophene in boron trifluoride diethyl etherate. The resultant copolymer presents multicolor electrochromism with reversible color change between drab color and blue black. Furthermore, in the polar state the resultant copolymer shows strong and broad absorption in the whole visible region and then exhibits black color. The copolymer presents a transmittance variation of 25% at 522 nm, and corresponding response times for bleaching and coloration are 4.2 and 3.3 s, respectively. Good electrochemical stability can be achieved by the copolymer film, which retains 87% of its original electroactivity after 2000 cycles.