Thermodynamic analysis of the growth of sodium dodecyl sulfate micelles

Abstract

A strong increase has been measured in the size and polydispersity of sodium dodecyl sulfate (SDS) micelles on increasing the detergent concentration in solutions containing high salt (NaCl) concentration. The mean hydrodynamic radius and the polydispersity of the micelles were measured. A thermodynamic theory of micelle formation and growth is presented. This theory makes use of the experimentally established result that the micelles have the shape of prolate spherocylinders. The micellar size and polydispersity is determined at each temperature and salt concentration by 2 chemical potentials. These are the chemical potential changes associated with transferring a detergent monomer from the solvent to either the cylindrical or spherical region of the micelle. Using only these 2 chemical potentials as parameters, one can predict accurately the hydrodynamic radius, the polydispersity, and the scattered light intensity over the entire experimental range of detergent concentration, temperature, and salt concentration. 43 references.