EFFECTS OF SHEAR-FLOW ON LONG-RANGED CORRELATIONS, SPINODAL DEMIXING KINETICS, AND THE LOCATION OF THE CRITICAL-POINT AND CLOUD POINT

A derivation of an expression for the shear rate-dependent Ornstein Ze rnike structure factor is discussed, together with the resulting anoma lous behavior of the turbidity. The predicted scaling behavior of the turbidity, comprising the effect of both temperature and shear rate, i s in good agreement with experiments on binary fluids. Then initial sp inodal decomposition is discussed, and an explicit expression for the time- and shear rate-dependent effective diffusion coefficient is deri ved, which shows all the typical characteristics of anisotropic light scattering patterns that are observed experimentally for binary fluids . Next it is shown that the spinodal is shifted linearly with the (bar e) Peclet number for not too large Peclet numbers, whereas the cloud p oint is singularly displaced into the unstable region due to a shear f low. This is in agreement with an experiment on a two-polymer/solvent mixture and binary fluid mixtures. It is argued that light scattering is useless to determine the location of the spinodal of a sheared syst em.