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 behav ior in aqueous media are studied by voltammetry, chronoamperometry, and oth er methods combined with IR spectroscopy and the tracer technique. The last two methods reveal that pyrrole molecules in acid media form complexes wit h protons and anions, and that a strong interaction occurs in a polypyrrole film between links of polypyrrole chains and anions, leading to a change i n their structure. The obtained data are used to propose a mechanism for th e synthesis of polypyrrole films, which includes the discharge of a complex of protonated pyrrole with the anion yielding radical cations, which induc e 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 f ormation during the discharge and partial destruction of the pyrrole comple xes with the anion.