Evidence of a Sponge-to-Lamellar Phase Transition under Shear by X-Ray Scattering Experiments in a Couette Cell

The L₃ sponge phase under shear in a Couette cell is totally transformed to a lamellar phase L_α* above some critical shear rate ̇ \.γc. In situ x-ray scattering and simultaneous light microscopy observations show that the first nuclei of the L_α* phase appear at a low critical shear rate ̇ \.γₐ and that the orientation of the lamellae in the L_α* phase tilts over from a so-called `` a'' orientation to a `` c'' orientation at ̇ \.γc. In the regime with two phases ̇ \.γₐ and ̇ \.γc, the phases are in an epitaxial relationship immediately after the shear is removed.