LONG-TERM REDOX SWITCHING STABILITY OF POLYPYRROLE

Polypyrrole (PP) films, including poly(pyrrole chloride) (PP-Cl), polypyrrole/poly(styrenesulfonate) (PP/PSS) and poly(pyrrole p-toluenesulfonate) (PP-TOS), were synthesized from various electrolyte/solvent systems. The films were subjected to potential cycling to equilibrate the electroactivity in various switching media. In most cases, the use of a different solvent from the synthesis medium strongly decreased the electroactivity of the PP. The effect of this solvent exchange was strongest in PP-Cl and relatively small in PP/PSS and PP-TOS. After equilibration, the films were subjected to multiple potential steps between the reduced and oxidized states while monitoring the charge passed. The electroactivity changes, measured as the amount of switching charge passed relative to the initial switching charge, were monitored with the number of double potential steps as a probe of the long-term stability. In general, the order of long-term switching stability of PP was determined to be PP-TOS>PP/PSS>PP-Cl, with each system exhibiting unique responses based on its electrochemical history.