Shear-induced orientations in a lyotropic defective lamellar phase

Abstract

The influence of shear on a defective lamellar phase of the ternary mixture sodium dodecyl sulphate/decanol/D2O was studied using small-angle neutron scattering (SANS), small-angle light scattering (SALS) and birefringence. Shear flow leads to an alignment of lamellae but in addition to previous studies, we found a reorientation from "perpendicular" lamellae, i.e. with the layer normal along the vorticity direction, to "parallel" lamellae with the layer normal along the velocity gradient direction at increasing shear rates. The reorientation processes were accompanied by a decrease of viscosity.