ELECTRONIC AND MAGNETIC-PROPERTIES OF POLYPYRROLE FILMS DEPENDING ON THEIR ONE-DIMENSIONAL AND 2-DIMENSIONAL MICROSTRUCTURES

We report on the electronic and magnetic properties of polypyrrole fil ms with a one-dimensional and two-dimensional microstructure. Polypyrr ole films as well defined and stable polymers are studied. The aim of this work is an explanation of the macroscopic conductivity based on m icroscopic and electronic structure. In particular we attribute the hi gh d.c. conductivity, the frequency-independent a.c. conductivity and the weak temperature dependence of the conductivity to the existence o f two-dimensional crosslinked areas. We characterize the polypyrrole f ilms by photoelectron spectroscopies (X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS)), by electron par amagnetic resonance (EPR) spectroscopy, and by the frequency-and tempe rature-dependent conductivity measurements. We compare the results to the corresponding propel-ties of one-dimensional polypyrrole films. Th e two-dimensional films consist of a graphitic electronic structure in which pyrrole monomers either contribute to the two-dimensional pi-sy stem or maintain their monomeric character, as characterized by photoe lectron spectroscopies. The EPR data reveal magnetic centers that show a Curie-like susceptibility and a weak Pauli contribution, and the la tter does not contribute to the conductivity mechanism. The EPR linewi dth is extraordinarily sharp and reversibly reflects the dynamics of t he interaction to oxygen. (C) 1998 Elsevier Science S.A.