Lyotropic structures in a thermotropic liquid crystal.
We have investigated the nature of didodecyldimethylammonium bromide (DDAB)/water aggregates dispersed in 4-n-pentyl-4'-cyanobiphenyl thermotropic liquid crystal (5CB). The structure of this microemulsion has been probed by small-angle neutron and X-ray scattering experiments far above the nematic-to-isotropic phase transition temperature of the solvent. Our data show that the stability of this system is controlled by strong attractive van der Waals interactions between 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 5CB paranematic fluctuations.
Toquer
Guillaume
G
Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587, CNRS-Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France.
Porte
Grégoire
G
Nobili
Maurizio
M
Appell
Jacqueline
J
Blanc
Christophe
C