Abstract
A time-resolved quasi-elastic laser-scattering method was applied to monitor the dynamic and collective behavior of molecules of an anionic surfactant, sodium dodecyl sulfate (SDS), around the critical micelle concentration (cmc) at several water/chlorinated hydrocarbon interfaces. The time courses of the capillary wave frequencies after injection of the SDS solutions into the water phase were investigated. We found that when the injected concentration is above the cmc, the relative number density of SDS molecules decreases with an increase in the bulk aqueous concentration at all the examined interfaces. We also found that the relative number density of SDS molecules adsorbed onto the interface increases with a decrease in the permittivity of the organic phase. Our results suggested that the adsorption of SDS molecules was affected by the permittivity of the organic phase.
