Properties of the three-phase bodies in water-oil-nonionic amphiphile mixtures

Abstract

The dependence of the properties of the three-phase bodies in ternary H20-oil-nonionic amphiphile mixtures on the nature of the oil and the amphiphile is of importance for both research and application.We suggest characterizing these properties by the coordinates 71* (temperature) and 7* (amphiphile weight fraction) of the amphiphile-rich phase (the microemulsion) at equal volumes of water and oil, as well as by the interfacial tension crabl between the aqueous and the oil-rich phase at this point of the phase prism. A relation between these properties is suggested that permits evaluating one of them if the other two are known. Furthermore, it is shown that the dependence of T* on the nature of the oil and the amphiphile is apparently correlated with that of the critical temperatures of the two binary mixtures oil-amphiphile and H20-amphiphile. The results are briefly discussed with respect to the currently proposed phenomenological models of microemulsions.

How to calculate phase diagrams for microemulsions — a simple rule

“…al. [3], x can be estimated from a calculation of the volume fraction of the hydrophilic head group compared to the volume of a single surfactant molecule. The values for the parameters R w mic l s -1 and a w can be determined from a fit of a section of a water-, and R oil mic l s -1 and a o from a fit of a section of an oil-emulsification boundary, respectively.…”

“…In conclusion we summarize the steps to be taken to arrive at the predictions for a specific choice of components: ⅷ Determine T l and T u from a fish cut at α = 0.5 [3]. ⅷ Estimate the value for x by calculating the volume fraction of the hydrophilic and hydrophobic part of a surfactant molecule.…”

“…In accordance with [5] we take the values ρ w = 0.998 g/cm 3 , ρ decane = 0.730 g/cm 3 , ρ octane = 0.702 g/cm 3 , ρ C 4 E 1 = 0.916 g/cm 3 , and ρC 12 E 5 = 0.967 g/cm 3 for the density of water, decane, octane, C 4 E 1 , and C 12 E 5 , respectively.…”

“…In mixtures of water, oil and a surfactant the amphiphilic molecules reside preferentially at the water-oil interface, in order to cope with the opposite preferences of the solubility of their head and tail. Extended internal interfaces are formed between water and oil domains, thereby also reducing the macroscopic interfacial tension substantially [2][3][4][5][6]. Shaking the mixtures may lead to the spontaneous formation of nanometer sized, thermodynamically stable microdomains of water and oil, separated by extended (≈100 m 2 /cm 3 ) internal interfaces.…”

Nonaqueous Microemulsions Containing Ionic Liquids – Properties and Applications

“…The phase diagram, where the mass fraction of surfactant is shown as a function of temperature, takes the shape of a fish. These so-called fish cuts are the most often used twodimensional phase diagrams concerning microemulsions with non-ionic surfactants and have been studied systematically for aqueous microemulsions by Kahlweit et al (Kahlweit et al, 1988;Kahlweit et al, 1989). Atkin and Warr presented fish-cuts obtained for an equal ratio of water to oil for surfactants with increasing amphiphilicity (C 8 E 2 , C 12 E 3 , C 14 E 4 ).…”