STRUCTURE EVOLUTION OF A POLYMER-SOLUTION AT HIGH-SHEAR RATES

We utilized large angle light scattering to study the structure of a s heared semidilute polymer solution. Below a critical shear rate gamma( c) we observe an enhancement of concentration fluctuations in accordan ce with previous experimental and theoretical work. Above gamma(c) we find dramatic changes in the transient and steady state scattering beh avior which indicate a shear-induced phase separation. A new four-peak ed structure which coarsens in time is observed which is superimposed upon the scattering characteristic of low shear. The four-peaked scatt ering structure evolves into two peaks along the gradient direction, i mplying the formation of phase-separated domains elongated along the s hear direction.