Structure and phase equilibria of microemulsions

We present a simple phenomenological model to describe the phase equilibria and structural properties of microemulsions. Space is divided into cells of side ξ; each cell is filled with either pure water or oil. Surfactant molecules are presumed to form an incompressible fluid monolayer at the oil–water interface. The monolayer is characterized by a size‐dependent bending constant K(ξ), which is small for ξ≥ξK, the de Gennes–Taupin persistence length. The model predicts a middle‐phase microemulsion of structural length scale ξ≊ξK which coexists with dilute phases of surfactant in oil and surfactant in water. (These phases have ξ≊a, a being a molecular length.) On the same ternary phase diagram, we find also two regions of two‐phase equilibrium involving upper‐ and lower‐phase microemulsions that coexist with either almost pure water or oil. At low temperatures and/or high values of the bare bending constant, K0≡K(a), the middle‐phase microemulsion may be entirely precluded by separation to a lamellar phase...

[1]  Kan Chen,et al.  Micro-emulsions in oil-water-surfactant mixtures: an Ising lattice gas model , 1987 .

[2]  Smith,et al.  Steric interactions in a model multimembrane system: A synchrotron x-ray study. , 1986, Physical review letters.

[3]  Roux,et al.  Origin of middle-phase microemulsions. , 1986, Physical review letters.

[4]  D. Roux,et al.  Modelling interactions in microemulsion phases , 1986 .

[5]  B. Widom,et al.  Lattice model of microemulsions , 1986 .

[6]  H. Kleinert.  Thermal softening of curvature elasticity in membranes , 1986 .

[7]  W. Helfrich.  Effect of thermal undulations on the rigidity of fluid membranes and interfaces , 1985 .

[8]  L. Peliti,et al.  Effects of thermal fluctuations on systems with small surface tension. , 1985, Physical review letters.

[9]  C. Taupin,et al.  Determination of the rigidity constant of the amphiphilic film in birefringent microemulsions: the role of the cosurfactant , 1985 .

[10]  Duane H. Smith,et al.  The role of critical points in the formation of coexisting liquids in the m-Xylene/water/i-C9H19C6H4(OC2H4)9.2OH-temperature trigonal prismatic diagram , 1984 .

[11]  B. Widom.  A model microemulsion , 1984 .

[12]  C. Taupin,et al.  Concentrated Winsor microemulsions: a small angle X-ray scattering study , 1984 .

[13]  D. Sornette,et al.  Repulsive steric interaction between membranes of finite size , 1984 .

[14]  K. E. Bennett,et al.  Toward understanding microemulsion microstructure: A small‐angle x‐ray scattering study , 1983 .

[15]  P. Gennes,et al.  Phase equilibria involving microemulsions (Remarks on the Talmon-Prager model) , 1982 .

[16]  J. Meunier,et al.  Critical behavior in microemulsions , 1982 .

[17]  P. G. de Gennes,et al.  Microemulsions and the flexibility of oil/water interfaces , 1982 .

[18]  Dinesh O. Shah,et al.  Surface Phenomena in Enhanced Oil Recovery , 1981 .

[19]  D. Langevin,et al.  Diffusion of interacting particles: Light scattering study of microemulsions , 1981 .

[20]  S. Prager,et al.  Statistical thermodynamics of phase equilibria in microemulsions , 1978 .

[21]  J. Wheeler,et al.  Phase transitions and critical points in a model three-component system , 1968 .

[22]  G. Gaines,et al.  Insoluble Monolayers at Liquid-gas Interfaces , 1966 .

[23]  N. Clark,et al.  Physics of complex and supermolecular fluids , 1987 .

[24]  S. Safran,et al.  Cylindrical microemulsions: a polymer-like phase ? , 1984 .

[25]  K. Mittal,et al.  Micellization, solubilization, and microemulsions , 1977 .

[26]  G. H. Brown.  Advances in Liquid Crystals , 1976 .

[27]  E. Ruckenstein,et al.  Stability of microemulsions , 1975 .

[28]  Hiroshi Saito,et al.  The effect of temperature on the phase equilibria and the types of dispersions of the ternary system composed of water, cyclohexane, and nonionic surfactant , 1968 .