Electron spin resonance studies of spin-labelled polymers—I segmental relaxation of polystyrene in solution

Abstract

From an analysis of the widths of the hyperfine lines in the ESR spectrum of a nitroxidelabelled polystyrene in toluene solution, the correlation times for rotational diffusion at three temperatures have been measured. The values agree well with published data from NMR studies of polystyrene in solution. The value of the activation energy for the relaxation process, 4·3 kcal. mole −1, is close to published values for dielectric relaxation of para-substituted polystyrenes. These comparisons provide strong evidence for associating the ESR correlation times with some form of segmental motion of the polymer backbone.