ESR STUDIES OF POLYPYRROLE FILMS WITH A 2-DIMENSIONAL MICROSTRUCTURE

Polypyrrole films with a defined two-dimensional structure are prepared by electrochemical polymerization. In as-prepared films, paramagnetic species are formed which have been investigated by electron spin resonance (ESR) spectroscopy. In the presence of oxygen the ESR linewidth of polypyrrole increases almost linearly with increasing oxygen pressure by a factor of more than 10 at atmospheric conditions. Oxygen exposure does not change the spin concentrations and does not influence the g factor of the paramagnetic centres in the polypyrrole layer. However, the ESR linewidth changes with oxygen pressures. Successive repetitions of oxygen exposure/pump-off procedures show an excellent reversibility. This reversible interaction of the paramagnetic centres in polypyrrole films with oxygen allows the application of these polymer films as oxygen sensors.