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The oxygen-induced ESR line broadening has been investigated in the case of the conducting polymer polyaniline in powder and in film form. Pumping under vacuum results in a narrowing of the ESR linewidth. After initial pumping various oxygen containing gases have been applied to the sample ͑pure O 2 , ambient air, dry air͒ and the linewidth has been measured as a function of time. The residual water in these gases was found to seriously affect the narrowing behavior of the linewidth. A theoretical calculation is proposed showing that the line broadening is proportional to the oxygen concentration and to the polaron mobility. Considering the linewidth dependence upon applied oxygen pressure an evaluation of the polaron mobility is obtained. This value is consistent with the values estimated from previous spin dynamics studies. An evaluation of the exchange integral is also given.

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The frequency dependences of both proton NMR T\ and ESR linewidth in polyaniline give evidence for quasi-lD spin diffusion. The on-chain diffusion rate, Z>n, is independent of the protonation level, while the transverse diffusion, D±, exhibits a sudden drop at the percolation threshold. This behavior confirms the conducting-island picture, but it is concluded that a given conducting island consists of just a single conducting chain. The room-temperature data show a strong correlation between spin dynamics and transport properties, and suggest that conductivity is governed by interchain hoppings.

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