Charge transport and spin dynamics of chemically synthesized polypyrrole soluble in organic solvents

The results of the temperature dependence of de conductivity, microwave dielectric constant, X-ray diffraction, EPR, and NMR experiments are reported for chemically synthesized polypyrrole films soluble in organic solvents. The temperature dependence of de conductivity of these systems follows the three-dimensional variable range hopping model. The slope of the temperature dependence of de conductivity varies with dopants and solvents used. Room temperature de conductivities are in the range of similar to 0.2-0.01 S/cm, and the localization lengths are estimated as similar to 10 Angstrom, which indicates a relatively strong localization of charge. The results of microwave dielectric constant experiments support the strong localization behavior. The X-ray diffraction studies show that soluble polypyrroles are amorphous. From electron paramagnetic resonance experiments, the density of states of polypyrrole doped with naphthalenesulfonic acid in m-cresol solvent is estimated as similar to 0.107 states/(eV ring). We obtain the result that the system achieves a more highly conducting state as the polarity of the solvent used increases.