Time-resolved small-angle neutron scattering study of shear-thickening surfactant solutions after the cessation of flow

Shear effects in dilute solutions of gemini surfactant solutions are studied by SANS in the shear-thickening regime. After the cessation of flow, the local anisotopy relaxes in about 10(2) s and we find evidence for a shear-induced change in the structure of the solutions that is stable for at least a few hours. The results can be understood if the shear-induced viscous phase is a loosely connected network of long-lived aggregates with typical size of 1 mu m. Counterions-mediated attraction between rodlike micelles could explain the formation of the aggregates and their long lifetime. The whole picture is consistent with previous results obtained for the same system using different techniques.