Structure Evolution of a Polymer Solution at High Shear Rates

We utilized large angle light scattering to study the structure of a sheared semidilute polymer solution. Below a critical shear rate γ̇c we observe an enhancement of concentration fluctuations in accordance with previous experimental and theoretical work. Above γ̇c we find dramatic changes in the transient and steady state scattering behavior which indicate a shear-induced phase separation. A new four-peaked structure which coarsens in time is observed which is superimposed upon the scattering characteristic of low shear. The four-peaked scattering structure evolves into two peaks along the gradient direction, implying the formation of phase-separated domains elongated along the shear direction.