Measurement and evaluation of polyaniline degradation

Abstract

The hydrolytic degradation of polyaniline (PANi) by electrochemical oxidation 1 m HClO4 is examined semi-quantitatively. It is suggested that the extent of degradation can be measured in terms of the incorporation of the hydrolysis products in the polymer matrix as evaluated by the ratio of the second anodic peak current to the first, iB iA, in the voltammogram of polyaniline (PANi) redox. The incorporation, in conjunction with partial polymer dissolution and subsequent thinning of the polymer deposit, fragmentation of PANi fibrils and extensive crosslinking, result in the densification of the polymer surface, loss of electrical conductivity and finally lead to the deactivation of the electrochemical activity. Two regions can be identified in the degradation process. In the active dissolution region, PANi is partially dissolved and a good fraction of the hydrolysis products is incorporated into the remaining film, changing both the morphology and the structure of PANi in due course. In the passivation region, the polymer is totally deactivated electrochemically as a result of the morphological modification. It is believed that degradation proceeds mainly in the surface layers of the polymer, resulting in low utilization of the polymer redox change in thick films and films deposited at high anodic deposition potentials. © 1993.