Influence of Shear on Lyotropic Lamellar Phases with Different Membrane Defects

The influence of shear on lyotropic lamellar phases in the system sodium dodecyl sulfate (SDS)/decanol/water has been studied using small angle neutron and light scattering (SANS, SALS), birefringence and rheology. Eight different samples with a constant water content of 67.4%, but different surfactant-cosurfactant ratio were studied. Static SANS measurements showed that replacing of SDS with decanol leads to a transition from a defective lamellar phase, characterized first by a ribbon like structure and then by a pore like structure, to a classical lamellar phase. An orientation diagram was obtained from SANS, SALS and birefringence measurements under shear. For samples with low decanol content, shear flow leads to an alignment of lamellae but in addition to previous studies, we found two reorientations, from a parallel (at low shear rates) to a perpendicular alignment of the lamellae (with respect to the walls of the shear cell) and to a parallel alignment again at the highest shear rates available. At ...