Oppositely charged surfactants have gained much attention in the fields of drug delivery, proton conductors, and cell membrane modeling. Much of the work has focused on miscible surfactant systems, where electrostatic interactions have influenced the phase behavior. Immiscible cationic-anionic surfactant systems have been less studied, but have recently been shown to stabilize oil/water mixtures via an unexpected mechanism. In our previous work, we stabilized a surfactant/fatty acid self-assembly formed at the interface between an aqueous cationic surfactant (cetylpyridinium chloride) solution and a fatty acid (oleic acid, OA). The nanostructured interface was characterized using interfacial rheology and small-angle X-ray scattering (SAXS). Here, we present the phase behavior of equilibrium bulk phases and established a ternary phase diagram for CPCl, OA and water. In the ternary diagram, we observed the formation of a gel phase at the equimolar mixing ratio of OA and CPCl similar to catanionic surfactant systems. A detailed comparison of bulk and interfacial materials characteristics is discussed. The phases of the bulk gel and the interfacial material exhibit similar viscoelastic and phase behavior, suggesting that the morphology of the interfacial gel is thermodynamically stable. The work presented here has implications in wide variety of complex fluid systems including surfactant mixtures, polymer solutions, emulsions, and colloidal domains.<br/>

Phase behavior of a stabilized surfactant/fatty acid self-assembly material

256th National Meeting (2018)

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