Exchange of the position of a spin probe in an aerosol OT reversed micelle

Abstract

The ESR spectra of a spin probe, (2,2,6,6-tetramethyl-4-piperidone- N-oxide, in degassed Aerosol OT reversed micelles containing various amounts of water in heptane solutions were measured over a wide temperature range. In a largely water-containing micelle, each line of the hyperfine structure splits into the doublet at low temperatures suggesting that the spin probe locates in two positions, the water pool and the shell formed by the surfactant molecules. The exchange rate between the two positions was calculated as a function of temperature using the modified Bloch equations, and the relationship between the micellar structure and the solution state of the probe was discussed on the basis of the hyperfine splitting constants and the intensity ratio of each line.