Electrochromism of Polyaniline Film Incorporating a Red Quinone 1‐Amino‐4‐bromoanthraquinone‐2‐sulfonate

A red quinone 1‐amino‐4‐bromoanthraquinone‐2‐sulfonate (BA) was electroreduced to produce the corresponding colorless dihydroxy compound. The peak potential separation for the electrode reaction of BA was drastically decreased by covering it with polyaniline film: ca. 0.8 V for a bare ITO electrode, ca. 0.1 V for the polyaniline film‐covered indium‐tin oxide electrode. This meant that the polyaniline film acted as an electrocatalyst for the reaction of BA. Furthermore, the positively charged nitrogens of the polyaniline polymeric chains incorporated the BA into the film. By changing the anodizing potential, the polyaniline film incorporating the BA (PANI‐BA film) exhibited a continuous variety of colors: colorless (0 V), green (0.2 V), and purple (0.3 V). The film retained the electrochromic properties of each component, and there was no undesirable interference. The switching time in the color change was found to be 100 ms. After 2 × 10 3 repititions, the polyaniline‐BA film still showed a bright color change. In addition, the color tone of the film was changed by the environmental solution pH.