KINETICS OF THE REEXTRACTION OF HYDROPHILIC SOLUTES OUT OF AOT-REVERSED MICELLES

Reversed micellar solutions, made of AOT in various nonpolar hydrocarbons and containing water, salt, amino acids, and/or chymotrypsin in their aqueous core were contacted with aqueous buffers with high ionic strength, thus evoking reextraction of the hydrophilic solute. The kinetics of these reextraction processes were measured by means of a two-phase stirred cell. The reextraction of all solutes was shown to be controlled by an interfacial process, and the reextraction rate was nearly independent of the solute. Water itself, however, was reextracted one to two orders of magnitude faster than the other solutes. These results are consistent with an interfacial-coalescence-controlling mechanism for solutes, the central step of which is the merging of the reversed micellar surfactant shell with the macroscopic interface. In contrast to this, an osmotic driven permeation mechanism is proposed for the fast reextraction of water, being characterized by diffusion of water through the AOT layers of micelle and macroscopic interface without exchange of salt. © 1992.