Abstract
We have investigated the nature of didodecyldimethylammonium bromide (DDAB)/water aggregates dispersed in4-n-pentyl-4¢-cyanobiphenyl thermotropic liquid crystal (5CB). The structure of this microemulsion has been probedby small-angle neutron and X-ray scattering experiments far above the nematic-to-isotropic phase transition temperatureof the solvent. Our data show that the stability of this system is controlled by strong attractive van der Waals interactionsbetween spherical inverted micelles. These interactions also explain why other swollen mesophases in related cosurfactant/DDAB/water/5CB phase diagrams are not observed. When approaching the isotropic-to-nematic phase transition,scattering experiments additionally confirm the predominance of an increasing attractive interaction due to the 5CBparanematic fluctuations.