Abstract
A spectroscopic technique of time-resolved quasi-elastic laser-scattering measurement was applied to monitor the dynamic and collective behavior of anionic surfactant sodium dodecyl sulfate (SDS) and neutral surfactant Triton X-100 molecules around their critical micelle concentrations (cmc's) at a water/nitrobenzene liquid/ liquid interface. The time courses of the capillary-wave frequencies after the injection of the surfactant solutions into the water phase were investigated. We found that the dynamic and collective behavior of these two kinds of surfactant molecules at the interface differ from that of the cationic surfactant cetyltrimethylammonium bromide we reported previously. Our results suggested that for SDS the monomolecules at the interface coexist with some molecular aggregates such as micelles at the interface; for Triton X-100, the monolayer at the interface was disrupted and some molecular aggregates, such as micelles, were formed at the interface.