Effect of Polymer Resistance on the Electrochemistry of Poly( vinylferrocene): Scanning Electrochemical Microscopic, Chronoamperometric, and Cyclic Voltammetric Studies

The electrochemistry of a poly(viny1ferrocene) (PVF) film of ca. 2100 8, was investigated in 1 M aqueous NaC104 solution with electrochemical and scanning microscopic techniques. The potential-step transients show well-defined maxima that a re very similar to those found for the electrochemical switching of electronically conductive polymers, e.g., polypyrrole and polyaniline. We explore here the possibility that the film resistance accompanying changes in the polymer oxidation state is a major factor in determining the shape of these transients. These chronoamperometric curves also allow the determination of an apparent diffusion coefficient. The scanning electrochemical microscope (SECM) has been used to penetrate the PVF film and to obtain directly the thickness of the film immersed in the electrolyte solution. Different shapes of the tip currentdistance curves are observed, depending on the oxidation state of the PVF film and its electrochemical treatment history. Mechanisms for the different approach curves a re suggested.