The lamellar-to-isotropic transition in ternary amphiphilic systems
Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Kantstr. 55, 14513
2 Sektion Physik der Ludwig-Maximilians-Universität München, Theresienstr. 37, 80333 München, Germany
Accepted: 29 August 1996
We study the dependence of the phase behavior of ternary amphiphilic systems on composition and temperature. Our analysis is based on a curvature elastic model of the amphiphile film with sufficiently large spontaneous curvature c0 and saddle-splay modulus sufficiently negative that the stable phases are the lamellar phase and a droplet microemulsion. In addition to the curvature energy, we consider the contributions to the free energy of the long-ranged van der Waals interaction and of the undulation modes. We find that for bending rigidities of order , the lamellar phase extends further and further into the water apex of the phase diagram as the phase inversion temperature is approached, in good agreement with experimental results.
PACS: 64.70.Ja – Liquid-liquid transitions / 64.75.+g – Solubility, segregation, and mixing / 82.70.-y – Disperse systems
© EDP Sciences, 1996