THE INFLUENCE OF IONIC CHARGES ON THE STRUCTURAL AND DYNAMICAL BEHAVIOR OF O W MICROEMULSION DROPLETS/

An O/W microemulsion system has been investigated where the droplet si ze can be controlled via the concentration of cosurfactant (1-hexanol) . In that system the charge density of the droplets was varied by subs titution of the original nonionic surfactant by a cationic surfactant. SANS measurements showed that the droplet radii are unaffected by the charging process, whereas the polydispersity decreases with increasin g charge density. SANS and also static light scattering experiments ar e well described by a simple electrostatic model, which renders this d roplet system a good model system. In contrast to that the diffusion c oefficient shows a somewhat more complicated behavior. It increases st rongly with rising ionic content but goes through a maximum around 3 m ol% ionic surfactant and then decreases again. The magnitude of the in crease and the position of the maximum are well described by theory, w hereas the steepness of the decrease at still higher ionic surfactant content is not accounted for.