Shear-Induced Isotropic-to-Nematic Phase Transition in Equilibrium Polymers

We report on a first-order isotropic-to-nematic phase transition induced by shear in concentrated solutions of elongated flexible wormlike micelles. As shear is applied to a disordered micellar solution, the transition shows up in steady-shear experiments as a kink in the shear stress behaviour. Using small-angle neutron scattering under shear, we show that beyond the transition rate, a nematic phase manifests itself by the growth of crescentlike scattering patterns in the direction perpendicular to the flow. A dynamical phase diagram is finally proposed for this system of equilibrium polymers.