(503i) A Direct Correlation between Recoverable Strain and Microstructural Evolution of Wormlike Micelles out of Equilibrium

Combining in-situ time-resolved small angle neutron scattering (SANS) and large-amplitude dynamic shear rheology, we show that the spatiotemporal evolution of micellar segments out of equilibrium is well correlated with the recoverable strain. The shear-induced alignment in both the velocity-gradient and velocity-vorticity planes is shown to be dictated by the recoverable strain, independent of the imposed frequency. The micellar system shows a distinct sequence of physical processes, beginning with linear viscoelastic behavior followed by softening/thinning and recoil, taking place twice per oscillation. Further, we demonstrate that the steady-state flow-curve and the linear-regime dynamic moduli can be constructed with the corresponding portions of the out-of-equilibrium LAOS response. The first normal stress difference is an open butterfly shape with total strain, but a simple parabola when plotted against the recoverable strain. This work provides a physical and straightforward path to further explore the microstructural evolution of self-assembled and polymeric materials under flow.