NMR spectroscopy was used to investigate micelle formation by a chiral surfactant. The surfactant contained a hydrocarbon tail attached to a leucine-valine dipeptide. Micelles formed by this surfactant have been used to separate the enantiomers in racemic mixtures. NMR diffusion experiments showed that in the pH range 7.0 to 11.5, the micelles had radii of approximately 25 Å. These radii agreed well with measurements from small angle neutron scattering. Below pH 9, lysine and arginine amino acids were found to bind to the anionic micelles. At higher pH values, though, both amino acids dissociated from the micelles. Finally, the dipeptide NH protons were observed to exchange with solvent protons. The rate of this exchange reaction was investigated along with the conformation of the surfactant’s dipeptide headgroup.

NMR investigation of micelle formation by a chiral dipeptide surfactant

251st National Meeting (2016)

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