ION-EXCHANGE AND MEMORY EFFECTS IN POLYANILINE

Memory effects in PANI can be promoted not only by holding the film at cath some time but also by cycling in a potential window with a reduced anodic limit. The peak overpotential of the first cycle after the pretreatment has a maximum for an anodic limit of +0.2 Vsce. The peak current presents a maximum value for an anodic limit of +0.12 Vsce and a minimum for +0.24 Vsce. Nonequilibrium effects are observed in the optical response of PANI. The optical absorbance at 440 nm during potential pulses shows a sharp maxima at short time an decays later to a constant value. The two redox steps of PANI oxidation involve mixed anion/proton exchange. For high proton concentration, protons are predominantly exchanged. At high pH (pH>2), an increase in the solution ionic strength brings about a bigger contribution of proton to the ion exchange process.