Dilute and concentrated phases of vesicles at thermal equilibrium

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.