Potential dependence of a number of the ‘residual’ spins in the electronically conducting polymer matrix

In situ electron paramagnetic resonance (EPR) and electrochemical measurements have been carried out for electrochemically prepared poly(1,5-diaminonaphthalene) in an acidic aqueous solution. The EPR intensity versus electrode potential dependence for this polymer cannot be explained on the basis of the commonly used model of polarons and bipolarons. The maximum of the EPR signal is observed for reduced form of the polymer; hence, the paramagnetic centers are not likely to be created during the oxidation process. We have proposed a model of spin recombination during the oxidation process which explains this unusual dependence of the EPR intensity.