DISCOTIC MICELLAR NEMATIC AND LAMELLAR PHASES UNDER SHEAR-FLOW

Small-angle neutron scattering was employed to study the effect of she ar flow on the nematic (N) and lamellar (L(alpha)) phases in aqueous s olutions of cesium perfluoro-octanoate. Shear rates as high as similar to 4000 s(-1) were used. The N phase was found to align with the dire ctor in the direction of the gradient velocity. The L, phase oriented with lamellae parallel to the shear plane. This change in equilibrium orientation is attributed, primarily, to changes in the value of the E ricksen viscosity parameter at. Subtle shear-rate-dependent director r eorientations were also observed in the proximity of the N-to-L(alpha) phase transition.