Electron Spin-Spin Interaction and Translational Diffusion of Nitroxide Radicals in Sodium Dodecyl Sulfate Micelles

Abstract

Abstract The line width measurements of ESR spectra of 2,2,6,6-tetramethyl-4-benzoyloxypiperidinyl-1-oxyl (BzONO) in sodium dodecyl sulfate (SDS) micelles have been carried out at various concentrations of BzONO. The plot of the line width against the concentration of BzONO shows a line with a break at mole fraction ca. 0.05, as opposed to the theoretical prediction that the plot would give a straight line. In order to explain this anomalous behavior, three models for the solubilization of BzONO are considered. On the basis of two of these models, spin exchange rates of BzONO in the micelles are estimated. Translational diffusion coefficients of BzONO in the SDS micelles at 20, 31, and 38.5 °C are calculated by using the spin exchange rate constants and an appropriate diffusion model. The obtained values are of the order of 10−7 cm2/s.