Electrical, magnetic, and structural properties of chemically and electrochemically synthesized polypyrroles

We report the results of temperature-dependent dc conductivity (sigma (dc)( T)) EPR (electron paramagnetic resonance) magnetic susceptibility, and XPS (X-ray photoelectron spectroscopy) experiments for chemically and electroch emically synthesized polypyrrole (PPy) samples. For chemically synthesized dodecylbenzenesulfonic acid (DBSA) or naphthalenesulfonic acid (NSA) doped PPy samples (PPy-DBSA or PPy-NSA, respectively) soluble in m-cresol solvent , de conductivity and its temperature dependence show the strong localizati on behavior, while those of electrochemically synthesized PPy doped with he xafluorophosphate (PPy-PF6) are in the critical regime. Pauli susceptibilit y (XP) and the density of states are obtained from the temperature dependen ce of EPR magnetic susceptibility. The density of states of chemically synt hesized PPy is one-third of that of electrochemically synthesized PPy. From the analysis of the area ratio of carbon Is XPS peak, the disorder effect due to interchain links or side chains of PPy-DBSA (m-cresol) samples is si milar to 22%, while that of PPy-PF6 samples is similar to 33%. This result indicates that the percent of interchain links or side chains of chemically synthesized PPy-DBSA (m-cresol) samples is reduced by similar to 10% compa red to that of electrochemically synthesized PPy-PF6 samples. We analyze th at the side chains or interchain links of chemically synthesized Pq, sample s are relatively reduced due to the synthesis method using large size dopan ts, and subsequently the interchain interaction weakens. The results of EPR experiments of PPy-DBSA (m-cresol) samples with different doping levels ar e discussed. (C) 2001 Elsevier Science B.V. All rights reserved.