Static and dynamic light-scattering study of solutions of strongly interacting ionic micelles

Abstract

Dilute solutions of ionic micelles formed by biological glycolipids (gangliosides) have been investigated at very low ionic strength by static and dynamic light scattering. With no added salt the effect of electrostatic interactions is so strong that both the scattered intensity and the measured diffusion coefficient are different by an order of magnitude with respect to the values obtained for weakly interacting micelles. The electric charge of the micelle is derived by a fit of the experimental structure-factor data which uses the hypernetted chain approximation for the radial distribution function. The dependence of the diffusion coefficient on the ionic strength is partially explained by considering, in addition to hydrodynamic interactions, effects due to the non-negligible size of the Na⁺ and Cl^– ions. The measured intensity correlation function deviates from exponential behaviour at extremely low ionic strength.