Electron Exchange Phenomena of Polymers Containing Nitroxyl Radicals

Abstract

The influence of electron exchange on the physical properties of polymers containing nitroxyl radical in their side chains has been studied by ESR, magnetic susceptibility measurement and cyclic voltammetry. ESR study shows that the electron exchange interaction between free radicals bound to a polymer chain is more effective than that between the corresponding monomeric radicals. Magnetic susceptibility (XM) was measured at temperatures between 4K and 273 K. The values of XM for the polymers obey the Curie-Weise Law (XM=c/(T−θ)), where magnetic moments obtained from XM show the presence of antiferromagnetic interaction between the nitroxyls of a polymer chain, although the interaction is not large enough to bring about long range ordering in the spin orientation of the nitroxyls. In the corresponding monomers, no antiferromagnetic interaction was observed. Cyclic voltammetry in DMF shows that the electrode process in polymer system is a reversible multiple-electron transfer reaction, where the number of the transfer (np) is 60% of the total free radicals per molecule. A comparison of the shape of the voltammetric response curve in the polymers with that in the corresponding monomers suggests that the interaction between nitroxyl radicals in the polymer is too weak to be reflected in electrochemical behavior.