We present a phenomenological theory for the dynamics of concentration fluctuations of polymer solutions in the presence of simple shear flow. A coupling between concentration fluctuations and stress exists in the system as a result of the concentration dependence of viscosity and normal stress coefficients. Linear analysis indicates that scattering is greatly enhanced by the flow, even at temperatures significantly above the equilibrium coexistence curve. This may explain experimental observations of turbidity above the equilibrium transition, but this would not be a true shift in the phase transition.

• Received 8 December 1988

DOI:https://doi.org/10.1103/PhysRevLett.62.2468