The shear-induced transition between oriented textures and layer-sliding-mediated flows in a micellar cubic crystal

A series of experiments has been performed in order to analyse the shear-induced structures for a micellar cubic phase using small-angle neutron and x-ray scattering techniques. Steady shear was applied in a Couette cell to the (EO)(127)(PO)(48)(EO)(127) triblock copolymer system dissolved in water. At rest, the system crystallizes into a long-range ordered mesophase of face-centred symmetry (lattice parameter similar to 300 Angstrom). The good resolution of the x-ray technique enables us to study in detail the transition between shearing flows dominated by oriented textures at law shear rates (gamma < 1 s(-1)) and flows mediated by the mechanisms of layer sliding at higher rates (gamma > 100 s(-1)).