FLOW-INDUCED MIXING AND DEMIXING IN POLYMER BLENDS

The effect of shear flow on the phase behaviour of partially miscible polymer blends exhibiting a lower critical solution temperature behaviour was investigated. Miscibility was detected, with and without the application of flow, as a change from optical clarity to turbidity using light scattering and as a shift in the glass transition temperature. Light scattering data were collected on a rheo-optical device that was designed to monitor phase changes in polymer blends undergoing shear flow between parallel glass plates in a temperature-controlled environment. Glass transition temperatures of quenched sheared blends were measured using a differential scanning calorimeter. It was found that shear-induced demixing and shear-induced mixing may be observed within the same blend depending on the magnitude of the applied flow. The magnitude of the increase or decrease in the lower critical solution temperature varied with the blend composition and also among the three blends used in this study.