Electron localization studies of alkoxy polyanilines

Substituted polyanilines, namely poly(o-methoxyaniline), poly(o-ethoxyaniline), and an equimolar blend of polyaniline and poly(o-methoxyaniline) were synthesized at various oxidant/monomer molar ratios with slow and fast addition of the oxidant. Electrical conductivity, magnetic susceptibility and electron spin resonance studies are reported for these polymers doped with the following acids: hydrochloric, para-toluene sulfonic, sulfosalicylic and trifluoroacetic. Results on thin films of camphorsulfonic acid doped poly(o-methoxyaniline) and polyaniline blends with poly(o-methoxyaniline) are also reported. A systematic study of these polymers shows that the conduction is due to quasi-one-dimensional variable range hopping. A Pauli-like susceptibility is seen in all the polymers indicating the existence of ordered regions. The electron localization length is found to be much larger in poly(o-alkoxyanilines) compared with the corresponding poly(o-alkylanilines). We propose that this effect arises from the electron-donating ability of the alkoxy group in contrast to the electron-withdrawing nature of the alkyl group. We also find that samples prepared with larger amounts of the oxidant are more disordered.