Electrochemistry of polypyrrole films in aqueous solutions: The character of the bond between the anion and the polymer matrix

Mechanisms of the formation and doping of polypyrrole films and their behavior in aqueous media are studied by voltammetry, chronoamperometry, and other methods combined with IR spectroscopy and the tracer technique. The last two methods reveal that pyrrole molecules in acid media form complexes with protons and anions, and that a strong interaction occurs in a polypyrrole film between links of polypyrrole chains and anions, leading to a change in their structure. The obtained data are used to propose a mechanism for the synthesis of polypyrrole films, which includes the discharge of a complex of protonated pyrrole with the anion yielding radical cations, which induce the growth and development of polypyrrole chains. It is stressed that the incorporation of anions into a film (doping) occurs in the course of its formation during the discharge and partial destruction of the pyrrole complexes with the anion.