UV-Vis./NIR and transport studies of chemically synthesized soluble polypyrrole

Doped polypyrrole which is soluble in various organic solvents (m-cresol, chloroform, DMSO, NMP etc.) is synthesized. Homogeneous solutions prepared from the solvents show different behaviors at near IR region depending on the solvent used. The results may be explained by PPy conformation change depending on polarity and aromatic interaction of solvents and dopants. Amorphous X-ray diffraction pattern is observed in flexible free standing films cast from these solutions. The electrical conductivity of the materials is 10−2 ~ 100 S/cm at room temperature. Temperature dependence of dc conductivity (σdc) indicates that these materials show the three dimensional variable range hopping (VRH) model and show the relatively strong localization of charge. From the EPR experiment of PPy-NSA (m-cresol) sample, the density of state of the system is estimated as ~0.06 states/eV ring.