Micromorphological dynamics of polypyrrole films in propylene carbonate solutions studied by in situ AFM and EQCM

Polypyrrole (PPy) films obtained by low-current galvanostatic polymerization of pyrrole in propylene carbonate solutions exhibit excellent reversibility, high anodic stability, and, at the same time, a characteristic change in the shape of the voltammetric response and an increase in the film's doping level during long-term potentiodynamic cycling. To understand the behavior of PPy films, we performed their characterization by in situ atomic force microscopy, which shows drastic changes in the micromorphology (and its dynamics) of freshly prepared and long-term cycled PPy films. In addition, a parallel study of the same PPy film was performed by electrochemical quartz crystal microbalance (EQCM), to correlate micromorphological changes in the films occurring as a result of continuous cycling with their ion-exchange mechanism. The morphological and mass changes are discussed in light of the fact that there are chemically different structures of PPy and in terms of a conformational relaxation model.