Experimental studies on phase separation in critical microemulsion and micellar systems

Abstract

We have studied the phase separation process in two systems containing surfactant molecules, i.e. a three-component microemulsion system made by a Aerosol OT-water-decane surfactant and a water-Butoxyethanol (C 4E 1) micellar-like mixture. The analyses were performed by using the time resolved light scattering intensity technique. All the three stages of the process were studied. The time evolution of intensities for the initial stage follows closely the linearized theory. Time evolution of the characteristic wave vector and the intensity distribution in the intermediate and late stages are in good agreement with scaling models. A comparison of the obtained data in the late stage with the findings of a recent Molecular Dynamic simulation, carried out in mixtures containing surfactant, gives a clear indication that in the investigated systems the phase separation process occurs through the formation of different structural coalesing domains. Whereas in the AOT microemulsion system the separation occurs through the formation of irregular bicontinuous-like domains, in the water-C 4E 1 mixture the separation is dominated by micellar domains which depend by thermal fluctuations.