AGGREGATION PHENOMENA IN WATER-IN-OIL EMULSIONS

We report the phase behavior of monodisperse water-in-oil emulsion dro plets. We show that depending upon the droplet size, the surfactant co ncentration within the continuous oil phase, the chemical nature of th e oil, and the temperature, the emulsion droplets may remain dispersed or reversibly aggregated. Close to the phase transition threshold, we observe coexisting phases, whereas much above, we preferentially obse rve gels. Since such phase transitions exhibit the same trends than wh at was previously observed in direct oil-in-water emulsions, a size pu rification process based on the same principles is accessible in the c oexisting regime. We present phase diagrams for two different droplet sizes that describe the main qualitative features of these systems.