Shear-induced discontinuous and continuous topological transitions in a hyperswollen membrane system

Here we demonstrate that both discontinuous and continuous transition between the sponge and lamellar phase can be induced by steady shear flow for a hyperswollen membrane system. The discontinuous nature of the transition is revealed by a distinct hysteresis in the rheological behavior between shear-rate increasing and decreasing measurements at a constant temperature. This discontinuity becomes weaker with an increase in the shear rate and temperature, and the transition eventually becomes a continuous one without any hysteresis. We also found another shear-induced transition in a one-phase lamellar region. The dynamic phase diagram in a nonequilibrium steady state under shear is constructed for the sponge-lamellar transition as well as another transition in a stable lamellar phase. Possible physical mechanisms for these shear-induced transitions are discussed.