We demonstrate here experimental evidence of the shear-induced sponge-to-lamellar transition in a hyperswollen lyotropic system. We also show that shear flow suppresses the first-order nature of the transition, especially above a critical shear rate. The phenomena are probably caused by two effects: (i) Symmetry-breaking shear field reduces large fluctuation effects associated with the degeneracy of the possible orientations of the ordered state. (ii) Shear flow favors the lamellar phase more than the sponge phase because the interconnected membrane structure obstructs flow. The sponge structure is destabilized for shear flow strong enough to tear off the passage of the membrane.

• Received 25 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.4390