Electron Spin Resonance Study of Intrinsic Paramagnetism of Soluble Polyaniline Perchlorates

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Abstract
An ESR study was carried out on two polyaniline perchlorates prepared by different chemical methods: Soluble perchlorate I prepared by the use of copper(II) perchlorate as an oxidative coupling agent, and perchlorate II (corresponding to polyemeraldine perchlorate) obtained by treating a polymer base with perchloric acid. The ESR signal intensity of perchlorate I shows a thermally activated temperature dependence at temperatures between 95 and 300 K. The ESR signal intensity of perchlorate II was temperature-independent. When this polymer adsorbed oxygen, the ESR signal showed a thermally activated paramagnetism resembling that of perchlorate I. These paramagnetic properties can be explained by polaron spins that are antiferromagnetically coupled with each other, and are different from the Pauli-type paramagnetism. This suggests that the charge-transport cannot be explained by the migration of paramagnetic polarons along a polymer chain alone.