NMR RELAXATION STUDIES OF INTERNAL MOTIONS - A COMPARISON BETWEEN MICELLES AND RELATED SYSTEMS

Multifrequency relaxation studies combined with the "two-step" model for molecular motion have shown striking similarities between correlation times for the fast motions at each of the last four carbons of aliphatic chains in surfactant and other systems. Determination of activation energies in nonsurfactant systems of 12 and 15 kJ mol-1 for the methyl and methylene groups, respectively, enabled correlation times for all data to be expressed at 298 K. The values for the correlation times are very similar, averages were 4.9, 11, 14, and 19 ps (starting with the methyl carbon), indicating similar molecular motions in micellar and nonmicellar systems. © 1990 American Chemical Society.