ELECTROCHEMICALLY PREPARED POLY(O-PHENYLENEDIAMINE) - PRUSSIAN BLUE COMPOSITE FILM FOR A 3-COLOR EXPRESSIBLE ECD MATERIAL

Both Prussian blue (PB) and poly(o-phenylenediamine) (PoPD) were easil y electrodeposited as stable films onto a transparent indium tin oxide (ITO) electrode. The voltammogram of the PB film showed a reversible sharp redox peak current at about 0.25 V. Although the colour change w as caused by altering the applied potentials, no colour change was see n after about 10(4) repetitions. The PoPD film also showed a reversibl e redox peak current at about -0.05 V. The redox reaction was accompan ied by a readily observable colour change between nearly red (vermilio n) and colourless. The PoPD film was electrodeposited onto the PB coat ed electrode to obtain a PB/PoPD composite film. The voltammogram of t he film was comprised of the two redox waves of the individual compone nts. The film retained the electrochromic properties of each component and there was no undesirable interference. By changing the potentials , the film exhibited a continuous variety of colours: colourless (-0.2 V), vermilion (0.1 V) and emerald green (0.6 V). The switching time o f the colour change was found to be <600 ms. Compared with the PB film , the composite film lasted longer. About 60% of the colouration remai ned after 10(5) repetitions since the PoPD worked as a binder which en hanced the adhesion of PB to the electrode surface.