Effect of electrolyte on the phase behavior and emulsion stability in the system didodecyldimethylammonium bromide (DDAB)/dodecane/water

• Published in: Journal of colloid and interface science 1992-08, Vol.152 (1), p.205-217
• Main Authors: Skurtveit, Roald, Sjöblom, Johan, Bouwstra, Joke, Gooris, Gert, Selle, Merete H
• Format: Article
• Language: English
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(92)90020-M

The DDAB/dodecane/water system has been studied with respect to phase behavior and emulsion stability, and the effects from added electrolytes have been investigated. The repeat distance in the lamellar liquid crystalline phase has been measured by X-ray scattering. Electron microscopy pictures of the lamellar phase reveal that thermodynamically unstable vesicles are formed in the pure phase, introducing a reduction in repeat distance. At low salinity and surfactant concentrations, a three-phase region L1 + L2 + D is found. Emulsions prepared in this three-phase region are extremely stable against coalescence. Upon addition of electrolytes, this three-phase equilibrium disappears and is replaced by a new three-phase region L1 + L2 + F and a reduction in emulsion stability is obtained. This reduction has been discussed with respect to several factors, including the change in curvature obtained for the surfactant film when electrolytes are added. At constant salinities, however, the existence of a hexagonal phase does not influence the stability of the emulsions.