Spinodal decomposition of a solution of a polymer mixture under shear flow

A semi-dilute solution of a polymer mixture which was phase-separated into two coexisting macroscopic phases in the quiescent state was subjected to a Couette-type shear flow. Anisotropic concentration fluctuations under steady-state shear, and their time evolutions in a transient relaxation process involved by rapidly changing the shear rates were studied by the time-resolved small-angle light scattering technique. The results clearly indicate that the weak shear enhances the coarsening rate. The effect of shear on the coarsening processes becomes significant in the time scale t>S-1, the distortion time by shear, or St>1.