MICELLAR FLUCTUATIONS IN A CALAMITIC NEMATIC PHASE OF A LYOTROPIC LIQUID-CRYSTAL STUDIED BY PHOTON-CORRELATION

Using a Rayleigh scattering light beating technique, we have made new measurements on the slow polarized fluctuations, previously identified as being of micellar origin, for a lyotropic system consisting of K-l aurate, decanol, D2O and presenting only the uniaxial calamitic nemati c (N(C)) phase (from among the three known nematic types: uniaxial dis k-like (N(D)), Calamitic (N(C)) and biaxial (N(B)) phases). An elabora ted analysis of these data is made in order to clarify the relationshi p between the light scattering signals coming from the micellar fluctu ations and those from (classical) orientational fluctuations. The main conclusions of this analysis are that the micellar mode is independen t of the temperature and wavevector, and that its relaxation frequency is substantially lower than that found previously for the same lyotro pic components, but presenting the biaxial nematic phase. Finally, som e considerations are made of the possible relationships between the mi cellar fluctuations and the structural properties of lyotropic nematic s.