SANS EXPERIMENTS ON MICELLAR NEMATIC MESOPHASES

Lyotropic Nematics are liquid crystalline mixtures characterized by an isotropic aggregates of amphiphilic molecules with finite shape and lo ng range orientational but no positional order. They are distinguished according to their macroscopic properties in positive and negative un iaxial nematics and in biaxial nematics. Very few notices are availabl e on the structure and on the evolution of the micelles through the di fferent nematic mesophases. We have studied by Small Angle Neutrons Sc attering the potassium laurate, decylammonium hydrochloride, water sys tem which was found to exhibit the three nematic phases as a function of temperature and concentration. SANS preliminary experiments were pe rformed at PAXY spectrometer of Orphee reactor at Saclay on adequate c ombinations of fully deuterated components.