Phase Behavior of Ternary Systems of the Type H₂OOilNonionic Amphiphile (Microemulsions)

Abstract

Liquid multicomponent systems of the type H,O-oil-amphiphile-electrolyte are of growing interest, both in industry and in research. In applications technology, there are two problems to solve: I. To prepare stable homogeneous solutions of H,O and nonpolar liquids with as little amphiphile as possible which can be diluted with H 2 0 in all proportions without phase separation; e.g., concentrated solutions of drugs, herbicides, or insecticides. 2. To prepare stable mixtures of an aqueous, an amphiphile, and an oil phase with as little amphiphile as possible which are employed in tertiary oil recovery and in the pharmaceutical industry. Furthermore, such systems may be used for performing chemical reactions in heterogeneous liquid mixtures with continuously variable properties. In research, such systems are of interest for both experimental and theoretical studies of critical phenomena, especially near so-called tricritical points. Last but not least, their properties may stimulate further research in the field of associated solutions. In this paper we summarize the results of our studies on the phase behavior of ternary systems with nonionic amphiphiles, in particular with respect to the evolution of liquid three-phase bodies. The results suggest that the tricritical points in such systems should be regarded as kinds of pivot points from which the phase behavior evolves. If this were an approach to reality, the phase behavior would be governed in more or less good approximation by universal scaling laws, irrespective of the particular microstructure of the solutions. Finally, we discuss the effect of electrolytes on the phase behavior both in a quaternary phase tetrahedron and a pseudoternary phase prism representation. Although in practice most systems consist of mixtures of oils, amphiphiles, and electrolytes, an understanding of the phase behavior of truly ternary and quaternary systems with chemically well-defined components permits at least qualitative predictions with respect to the phase behavior of the multicomponent mixtures encountered in practice.

Spontaneous Emulsification of Oils Containing Hydrocarbon, Nonionic Surfactant, and Oleyl Alcohol

“…It has an unconventional form. The L 1 /ME/L 2 region does not terminate as surfactant concentration is increased at a junction with a single-phase microemulsion region, the behavior found in most systems (12) including the present one with n-octanol replacing oleyl alcohol (7), nor is it like the systems with rather rigid surfactant/ alcohol films where a four-phase L 1 /L ␣ /ME/L 2 region extends to low surfactant concentrations (13,14). Instead the L 1 /ME/L 2 region apparently terminates in a small four-phase region as indicated by a question mark in Fig.…”

Ionic Liquids in Microemulsions—A Concept To Extend the Conventional Thermal Stability Range of Microemulsions

“…96,97,98 This led to a better understanding of the phase behavior of C i E j surfactants, oil and water. Kahlweit et al 98 presented the temperature dependent phase diagram by vertically stacking the Gibbs triangles into a prism, with temperature on the vertical ordinate.…”

“…96,97,98 This led to a better understanding of the phase behavior of C i E j surfactants, oil and water. Kahlweit et al 98 presented the temperature dependent phase diagram by vertically stacking the Gibbs triangles into a prism, with temperature on the vertical ordinate. Such a phase prism is shown exemplarily in Figure II for a given oil the three phase temperature interval lies lower, the more hydrophobic the surfactant and for a given amphiphile it lies higher the more hydrophobic the oil.…”

Microphase and Macrophase Separation in Multicomponent A/B/A−C Polymer Blends with Attractive and Repulsive Interactions

“…The C block is designed to have attractive interactions with the B homopolymer and repulsive interactions with the A homopolymer. This is analogous to surfactants for oil/water systems [42][43][44][45][46][47] wherein the hydrophilic portion of the surfactant exhibits attractive interactions with water and repulsive interactions with oil. In A/B/ A-C mixtures, surfactant behavior is governed by both attractive and repulsive interactions.…”