Conductive polymers, such as polyaniline, polypyrrole etc. have special chemochromatic properties. The redox processes in electrochemical cells are reversible and causes colour changes on the electrode covered by the polymer layer. The redox state of the polymer (with varying conductivity) can be changed either by chemical or electrical processes. The former method is used in sensor applications, the latter in actuator and display devices. The oxidised and reduced forms of polyaniline have different colour. Between the two states, its absorption spectrum changes continually from translucent to yellow, green, and blue, depending on the applied cell voltage. This voltage allows us to create low-power display devices, because the change is caused by transient processes and low current flow. The present study shows the details of these colour changes in polyaniline samples. By expanding the system with polymers with other spectra (e.g. o-phenilene-diamine with a spectrum from translucent to red) we might produce an RGB or CYM display.
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