Electron paramagnetic resonance study of intrinsic paramagnetism in poly(aniline trifluoromethanesulfonate), [(—C6H4NH—)(CF3SO3)0.5·0.5H2O]x

Abstract

An electron paramagnetic resonance (EPR) study has been carried out on poly(aniline trifluoromethanesulfonate)(abbreviated as triflate), [(—C₆H₄NH—)(CF₃SO₃)_0.5·0.5H₂O]_x, which contained a very small number of defect spins. The temperature dependence of the EPR signal intensity showed that two different spin species were involved in the polymer: one (denoted TA-spin species) exhibited a thermally activated paramagnetism and the other (C-spin species) showed a Curie-type paramagnetism. The EPR signal of the TA-spin species was motional-narrowed at ca. room temperature and broadened rapidly with decreasing temperature; this spin species is attributable to a trapped polaron, which is antiferromagnetically coupled to a neighbouring one. The EPR signal of the C-spin species underwent motional-narrowing with a maximum slope width of ca. 0.3 G throughout the temperature range investigated (18–300 K). A Pauli-type paramagnetism was not observed; the conduction band of polyaniline is too narrow to show the Pauli paramagnetism.