New insight on local electronic transport properties of poly(aniline): A comparative study of oligo(aniline) model compound and polymer using spin dynamics techniques

Abstract

Several spin dynamics techniques (ESR linewidth variation as a function of applied oxygen pressure and temperature, NMR relaxation time frequency dependence) have been used to comparatively investigate the electronic transport properties of HCl doped poly(aniline) and HCl doped tetra-aniline at a nanoscopic scale. DC-conductivity measurements and X-ray diffraction have also been carried out. From the data, the following conclusions can be derived: (i) at room temperature, the effective polaron hopping frequency at the nanoscopic scale, is one order of magnitude higher in the polymer than in the tetramer, (ii) new data support the Elliott mechanism as the origin of the ESR line broadening at high temperature and therefore bring a clear evidence in favor of the existence of a metallic state in the polymer. No evidence for such a metallic state exist in the tetramer. (iii) the polaron diffusion frequency appears to be highly anisotropic in both systems.