Alternating vorticity bands in a solution of wormlike micelles

We report on structural characterization of vorticity bands formed in a wormlike micellar solution by Rheo-small-angle neutron scattering and video imaging experiments. Below a critical shear stress tau(c) in Newtonian and shear-thinning regime, only a minor flow alignment of the micelles is observed. Above tau(c), in the shear-thickening regime, alternating transparent and turbid bands are formed. Triggered small-angle neutron scattering shows different anisotropic patterns in both bands indicating strongly aligned structures. By high-speed video imaging, we show that such an alignment of micelles does not correspond to a phase of lower viscosity.