On the Nature of Interaggregate Interactions in Lyotropic Liquid Crystalline Phases

The mesogenic unit of lyotropic nematic liquid crystals is either a columnar (NC) or discoid (ND) micelle. There is growing evidence that these micelles exist as discrete entities in both the isotropic phase and for disk shaped micelles, in the lamellar phase bounding the nematic. Here, the evolution of micelle size as measured by X-ray scattering from orientated samples of caesium perfluorooctanoate/water, has been followed as a function of concentration and temperature across all three phases. The micelle size is found to initially increase with increasing amphiphile concentration, but to decrease at higher concentrations. This behaviour is shown to be consistent with an attractive interaggregate interaction.