Microscopical structure of the uniaxial and biaxial lyotropic nematics

Abstract

High-resolution x-ray measurements have been performed at the synchrotron of LURE (Orsay) to study both uniaxial (discotic and calamitic) and biaxial nematic lyomesophases of the mixture K-laurate, 1-decanol, and D2O. The variations of the densitometric profiles of the diffracted bands are analyzed vs temperature. They are shown to be consistent with the model of similar micellar aggregates in the three nematic phases, undergoing different orientational fluctuations. It is moreover discussed that the micelles have, on the average, the shape of biaxial platelets with a (1/2/3) anisotropy, and that they build the same pseudolamellar structure in each nematic phase.