Effect of the nature of the electrolyte on the properties of unpaired spins in polyaniline

An extended study has been carried out to find the relation between the number of spins, the applied potential and the charge of the doping anion in the case of polyaniline electropolymerized in 5 M tetrafluoroboric acid. It was found that in the presence of acids which supply double-charged anions, a fast recombination of polarons to bipolarons occurs. This is in contrast to single-charged anions which stabilize polarons. Three types of spins were detected in the study: (i) localized spins, formed at the beginning of the oxidation process; (ii) mobile spins existing in the presence of single-charged anions; (iii) spins localized mostly at structural defects.