Analysis of the characteristics of electrochemically polymerized polypyrrole films by using QCA and AFM

In order to investigate dynamic properties of polypyrrole (Ppy) thin films in various electrolyte solutions, NaCl, NaClO4, NaNO3, NaDS, LiClO4, KClO4, resonant frequency and resistance were measured through electrical polymerization process using a quartz crystal analyzer (QCA). The surface structure was observed by using atomic force microscopy (AFM). A diagram of the resonant frequency and resistance (F-R diagram) was used to interpret the results and compared with AFM photograph. When the Ppy film is polymerized onto the AT-cut quartz electrode crystal, it behaves as a rigid elastic layer at the initial stage. Then, it turns into a viscoelastic layer as polymerization. This is due to the penetration of electrolytes into the film. The size, mass and mobility of the hydrated cation and anion of the electrolyte affected the degree of the viscoelastic change of the polypyrrole thin films.