On the Existence of a Stress−Optical Relation in Immiscible Polymer Blends

Abstract

In emulsions and immiscible polymer blends linear conservative dichroism is known to be very sensitive to flow-induced microstructural changes during flow. The same holds for the excess or interfacial contribution to the first normal stress. Similarities have already been observed between these two properties in blends. Here it is investigated whether this similarity reflects a more quantitative relationship. The interfacial normal stress can be described by means of an interface anisotropy tensor. Therefore, the measured dichroism will be compared with the calculated components of this anisotropy tensor for different flow histories. These include steady-state shear flow, sudden increase in shear rate, relaxation with droplet breakup, and oscillatory flow. In all cases a proportionality factor is obtained. For strongly deformed droplets direct theoretical evidence for a quantitative relationship between rheology and rheo-optics in blends is provided. To extend this relationship to a larger window of shear...