Lamellar systems which are close to microemulsions in the phase diagram are observed for the first time by quasielastic light scattering. The observed hydrodynamical mode is attributed to the collective undulations of the lamellae and allows us to determine the rigidity constant of the interfacial film. The results emphasize the role of the cosurfactant (alcohol) in the transition from organized phases (lamellar and birefringent) towards isotropic phases (droplet microemulsions).

• Received 4 January 1985

DOI:https://doi.org/10.1103/PhysRevLett.54.1686