Evolution of Physical and Electrochemical Properties of Polypyrrole during Extended Oxidation

The charge storage capacity and electrical conductivity of polypyrrole are followed through regimes of chemically reversible and irreversible electroactivity. Overoxidation of polypyrrole occurs at potentials in excess of 0.7 V vs. a saturated calomel electrode (SCE), as demonstrated by cyclic voltammetry of thin films. Material loss from polymer films as they are overoxidized is determined by in situ quartz microbalance experiments. The potential window for reversible electrochemistry in polypyrrole is compared to that for other conducting polymers. Reflectance FTIR of thick films reveals that hydroxyl groups, followed by carbonyls, result from overoxidation.