Degradation Kinetics of Polypyrrole Films

Abstract

Kinetic measurements have been made on the degradation reaction of electrochemically prepared polypyrrole films. The measurements were made by applying proper potentials at po lymer film covered electrodes in aqueous sulfuric acid solutions and monitor ing the absorbance of the electrolysis product as a function of time. Parameters included for the study were: the potentials at wh ich the films were made, degradation potential, acid concentration, and film thickness. Fi lms degrade faster at higher degradation potentials, in higher acid concentrations, and for thinner films. When the films are prepared at higher potentials than 1.30 V, they are much more stable, suggesting that polymers prepared at higher electrode potentials may have different structures and/or morpho logy f rom those prepared at lower potentials. Conduct ing polymers including polypyrrole (PPy), polyaniline, and polythiophenes, as well as their deriva-tives, have been receiving attention due to their possible applications as battery electrodes, electroehromic devices, chemical sensors, etc. 1-7 Most of these applications require repeated injection and removal of charges by doping-un-doping processes. The doping process, wh ich is accom-