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A quaternary system made of an ionic surfactant (SDS), octanol, water and sodium chloride has been investigated. We present experimental results that demonstrate the existence of a phase of vesicles at thermal equilibrium. We show that vesicles can be prepared both in a dilute regime leading to an isotropic liquid phase of low viscosity and in a concentrated regime leading to a phase of close packed vesicles (probably multilayered) exhibiting high viscosity and viscoelasticity

We report on the effect of a hydrosoluble neutral polymer on the stability of a lamellar phase made of charged surfactant bilayers. In the system investigated, the smectic structure exists for a wide range of dilutions, with smectic periods continuously varying between 30 and 300 I. Our results show that the lamellar The eventual presence of critical points on the border of the closed-loop smecticsmectic miscibility gap is investigated 1.

Anomalous flow birefringent phases, sometimes designated as L3, have been identified in both the water-rich and the oil-rich parts of the phase diagram of the water(NaCl)-dodecane-pentanol-SDS system. The presence of these phases appears to be associated with that of swollen lamellar phases. Conductivity and neutron scattering results provide evidence that the structure of these phases consists of a highly connected, spongelike, random bilayer-continuous surface. The surfactant surface separates, depending upont the system, either two water-continuous domains or two oil-continuous domains. The data are consistent with a recent theoretical models.

New light-scattering data from an anomalous isotropic phase in a bilayer-forming surfactant system (sponge phase) are analysed using a Landau-Ginzburg theory with two fluctuating order parameters: one the surfactant density, and the other associated with an “inside/outside” (I/O) symmetry that arises in bilayer-containing systems. The scattering shows a clear signature of this additional order parameters. The concentration dependence of the osmotic compressibility provides strong evidence for fluctuation-induced logarithmic corrections to the elasticity and/or area parameters of the bilayer.

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