Charge transport and electron localization in polyaniline derivatives

Electrical conductivity, magnetic susceptibility, and electron-spin-resonance studies are reported in polyaniline and its derivatives poly(o-toluidine), poly(o-ethylaniline), and poly(o-propylaniline). It is shown that substituents on the ${\mathrm{C}}_6$ rings of the polymer backbone lead to decreased conductivity, decreased Pauli susceptibility, and an increased number of Curie spins. Also reflecting these features are electron-spin-resonance line shapes, which transform from Lorentzian for polyaniline toward Gaussian for poly(o-propylaniline). These results are interpreted in terms of increased electron localization caused by increased interchain disorder. Furthermore, evidence of electron-electron correlations is presented for poly(o-propylaniline).