Spin dynamics in the conducting polymer, polyaniline

The frequency dependences of both proton NMR $T_1$ and ESR linewidth in polyaniline give evidence for quasi-1D spin diffusion. The on-chain diffusion rate, ${\mathit{D}}_{\mathrm{\parallel }}$, is independent on the protonation level, while the transverse diffusion, $D_{\perp }$, exhibits a sudden drop at the percolation threshold. This behavior confirms the conducting-island picture, but it is concluded that a given conducting island just consists of 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.