An electron paramagnetic resonance study of poly(isothianaphthene)

Electron paramagnetic resonance (EPR) and electrical conductivity are studied in undoped, iodine- and Cu(II) complex-doped poly(isothianaphthene) (PITN) powders prepared by O-2-induced polymerization of 1,3-dihydroisothianaphthene. The integrated intensity of the EPR signals of iodine- doped PITN increases as the dopant concentration increases up to 5%, then decreases, while the conductivity shows a sharp increase at a doping level of about 9%. The EPR linewidth decreases slightly upon dedoping and increases as the doping level increases. These results are discussed in terms of the formation of polarons and bipolarons and a transition from a semiconductor to a metallic regime upon doping. PITN samples doped with three different anionic Cu( II) complexes by an ion-exchange process show a Cu( II) doping level that is 3 5 times greater than that in samples prepared by a direct doping process. Cu(II) complex-doped PITN (sigma(max) = 5.2 S cm(-1)) gives better conductivity than iodine- doped PITN (sigma(max) = 0.16 S cm(-1)) even at lower doping levels. This is possibly due to an increase in the interchain contribution to the conduction mechanism.