Electrochemical degradation of polyaniline in HClO4 and H2SO4

The ratio of the sum of the second and third anodic current peaks to the first anodic current peak, (Ip,B1 + Ip,B2)Ip,A, in the cyclic voltammogram of polyaniline in H2SO4, was used to measure the extent of polymer degradation that occurs during electropolymerization. Structural determination by UV-Vis spectroscopy and morphology examination by scanning electron microscopy verified that a large ratio is indicative of a more extensive degradation. The ratio was found to vary with the number of deposition cycles. It decreased initially to a minimum and then increased to a steady state value. It is postulated that the initial decline was caused by a transition in the reaction mechanism for radical-cation generation, whereas the increase after the minimum was caused by ion-pair formation between sulfate anions and the polymer chains. Mass transfer limitation eventually set in, leading to the saturation of the ratio at the steady state value.