Li+ doping-induced localization in polyaniline

We report that LiCl dopes the emeraldine base (EB) form of polyaniline and produces polyaniline with unusual properties—polyaniline with doping-induced charge localization. Our assignment of Li+ doping is based upon the observation of electronic states in the bandgap and associated spins for EB processed with LiCl. However, even at the maximum doping level, LiCl-doped polyaniline is a strongly localized charged insulator based on the observation of low DC conductivity, low dielectric constant, rapid decrease of the oscillator strength to zero in the infrared, low magnetic susceptibility dominated by a weak Curie component, broad EPR linewidth and predominantly Gaussian lineshape of the EPR signal. Finally, we attribute these properties to the formation of bipolarons or antiferromagnetically coupled polaron pairs in LiCl-doped EB.