ESR STUDIES OF POLYPYRROLE FILMS WITH A 2-DIMENSIONAL MICROSTRUCTURE

Polypyrrole films with a defined two-dimensional structure are prepare d by electrochemical polymerization. In as-prepared films, paramagneti c species are formed which have been investigated by electron spin res onance (ESR) spectroscopy. In the presence of oxygen the ESR linewidth of polypyrrole increases almost linearly with increasing oxygen press ure by a factor of more than 10 at atmospheric conditions. Oxygen expo sure does not change the spin concentrations and does not influence th e g factor of the paramagnetic centres in the polypyrrole layer. Howev er, the ESR linewidth changes with oxygen pressures. Successive repeti tions of oxygen exposure/pump-off procedures show an excellent reversi bility. This reversible interaction of the paramagnetic centres in pol ypyrrole films with oxygen allows the application of these polymer fil ms as oxygen sensors.