EPR AND CHARGE-TRANSPORT STUDIES OF POLYANILINE

The study of dc and microwave (140 GHz) electrical conductivities usin g multifrequency electron-spin resonance in undoped and HCl-hoped poly aniline is reported. The accidental quasi-three-dimensional (3D) charg e hopping between the pinned and mobile small polarons dominates the b ulk conductivity of the emeraldine base form of polyaniline. The incre ase in mobility and the number of excitations upon light doping of the polymer leads to the isoenergetic interpolaron charge hopping between the polaron and bipolaron states. 1D variable-range hopping of a char ge between conducting islands, which correlates with a superslow torsi onal dynamics of the polymer chains, dominates bulk conductivity bf he avily doped polyaniline at low temperatures. Intrinsic microconductivi ty is determined by the interaction of the charge with the lattice pho nons at high temperatures. Following Epstein and MacDiarmid we propose that emeraldine salt of polyaniline represents a 1D disordered conduc ting compound consisting of metal-like islands of well coupled chains with 3D delocalized charge carriers.