Shear-induced effects on miscibility in polymer solutions

Methods of macromolecular integral equation theory are employed to calcuate the correlation functions of flexible linear homopolymers deformed by shear flow. The extent of coil deformation is calculated from bead-spring models that include corrections for finite chain extensibility and pre-averaged hydrodynamic interactions. The spinodal boundaries for sheared polymer solutions are obtained from the compressibility route under conditions of constant strain rate. It is shown that accounting for changes in the cohesive energy arising from flow-induced coil deformation may lead to non-monotonic shifts in the cloud point as a function of applied shear, even in the absence of nonlinear viscoelastic response. These model calculations are compared with experimental measurements of the cloud point for sheared solutions of polystyrene in dioctyl phthalate.