Critical Behaviour of Lyotropic Liquid Crystals

Abstract

The occurrence of a critical point in lyotropic smectic liquid crystal is experimentally evidenced by neutron and X-ray small-angle scattering experiments. In the vicinity of the critical point in the (c-T) phase diagram of a true binary system, we observe: 1) broadening of the Bragg peak of the coexisting lamellar phases; 2) strong scattering at small angle where the concentration and periodicity difference between the two phases (Lα) in equilibrium vanishes. First approximate values of the critical exponents are given.