Publication

Abstract : X-band electron spin resonance (ESR) of polyaniline (PANI) doped with 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPSA), at conductivity values of 90, 4, and 0.2S cm, has been investigated from 300to5K. Free-standing films (30-40μm thick) of PANI were prepared by solution casting method. The spectra consist of two signals, one is broad (∼60G) and the other is narrow (∼10G), at nearly the same resonance field. The temperature variation of ESR susceptibility indicates a stronger Pauli component in the broad line signal, as compared to the narrow signal, at all values of conductivity. Both linewidths are independent of the presence of O2. The temperature variation of linewidths is explained in terms of the quasi-two-dimensional (Q2D) model. These results suggest that in some regions the doped PANI chains have self-assembled Q2D structure, and the presence of a significant Pauli susceptibility indicates that the charge carriers are highly delocalized in these Q2D regions. © 2005 The American Physical Society.