Shear-induced sponge-to-lamellar phase transition studied by rheo-birefringence

We report on the shear induced transition from the L₃- to the L-phase studied by means of flow birefringence using the system pentaethyleneglycol monododecylether (C₁₂E₅), decane, water. The dependence of the critical shear rate, at which the transition from the isotropic state to the anisotropic takes place, on membrane volume fraction was studied in temperature ramp experiments at different constant shear rates and in isothermal shear ramp experiments. These results are compared with relaxation experiments from the shear aligned state back to the isotropic. For all these experiments power law exponents in the membrane volume fraction between 1.6 and 2.8 were found, which are rather low compared to values of current theories. The values found for the inverse critical shear rate and the decay times from the relaxation experiments differ by four orders of magnitude.