Charged o/w microemulsion droplets

Structure and properties of charged oil-in-water (o/w) microemulsions have been investigated. A particular system made up from a zwitterionic surfactant and hydrocarbon which becomes charged upon the addition of either cationic or anionic surfactant has been studied. A particular feature of this microemulsion system is that the charge density on the droplets can be fixed at a desired value in an easily controllable fashion. These systems have been characterized by means of light scattering, SANS, interfacial tension measurements, electric conductivity and viscosity measurements. The experiments showed that the aggregates remain constant in size over a large concentration region, i.e., from 0.1 to 30 wt%. Moreover, their size is not much changed by the addition of the ionic surfactant. The interactions in this microemulsion system could be described by a hard sphere interaction with an additional DLVO — potential term that accounts for the electrostatic repulsion.