Quasielastic neutron scattering measurements of monomer molecular motions in micellar aggregates

Quasielastic neutron scattering measurements have been made on some micellar aggregates. It is shown that the observed spectra arise almost exclusively from monomer motions in the aggregates. Two illustrative systems were studied, direct micelles of tetradecyl trimethyl ammonium bromide in water, and reverse micelles of aerosol OT in cyclohexane with different amounts of water solubilised inside the micellar core. For the aerosol OT micelles, the translational diffusion is fast (8×10^?10 m².sec^?1) and independent of the size of the water pool. Rotational correlation times are of the order of 4×10^?11 sec. At high water contents the water in these pools is similar to bulk aqueous electrolytic solutions. For the tetradecyl trimethyl ammonium bromide micelles the translational diffusion constant was found to be 5×10^?10 m².sec^?1.