Microscopic Parameters of Sodium Dodecyl Sulfate Micelles from Optical Probe Studies and Quasi-Elastic Light Scattering

Abstract

Quasi-elastic light-scattering measurements of the diffusion of sodium dodecyl sulfate (SDS) micelles in aqueous solutions, and the diffusion of mesoscopic optical probes through the same solutions, were carried out at 35 °C and multiple solvent ionic strengths. From nonlinear least-squares fits to both probe and mutual diffusion data, assuming a spherical micelle, we deduced the micelle radius, aggregation number, charge, and hydration. For SDS micelles the charge that we find is lower than that in the literature (Hayter, J. B.; Penfold, J. Colloid Polym. Sci. 1983, 261, 1002. Triolo, R.; Caponetti, E.; Graziano, V. J. Phys. Chem. 1985, 89, 5743); the difference arises because we use an improved form for the intermicellar electrostatic potential. As further results of using the same potential, we find a smaller aggregation number and a larger micellar hydration than those reported in the literature.