MEASUREMENT AND EVALUATION OF POLYANILINE DEGRADATION

The hydrolytic degradation of polyaniline (PANi) by electrochemical ox idation 1 M HClO4 is examined semi-quantitatively. It is suggested tha t the extent of degradation can be measured in terms of the incorporat ion of the hydrolysis products in the polymer matrix as evaluated by t he ratio of the second anodic peak current to the first, i(B)/i(A), in the voltammogram of polyaniline (PANi) redox. The incorporation, in c onjunction with partial polymer dissolution and subsequent thinning of the polymer deposit, fragmentation of PANi fibrils and extensive cros slinking, result in the densification of the polymer surface, loss of electrical conductivity and finally lead to the deactivation of the el ectrochemical activity. Two regions can be identified in the degradati on process. In the active dissolution region, PANi is partially dissol ved and a good fraction of the hydrolysis products is incorporated int o the remaining film, changing both the morphology and the structure o f PANi in due course. In the passivation region, the polymer is totall y deactivated electrochemically as a result of the morphological modif ication. It is believed that degradation proceeds mainly in the surfac e layers of the polymer, resulting in low utilization of the polymer r edox change in thick films and films deposited at high anodic depositi on potentials.