On the existence of a stress-optical relation in immiscible polymer blends

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 firs t normal stress. Similarities have already been observed between these two properties in blends. Here it is investigated whether this similarity refle cts a more quantitative relationship. The interfacial normal stress can be described by means of an interface anisotropy tensor. Therefore, the measur ed dichroism win be compared with the calculated components of this anisotr opy tensor for different flow histories. These include steady-state shear d ow, sudden increase in shear rate, relaxation with droplet breakup, and osc illatory flow. In all cases a proportionality factor is obtained. For stron gly deformed droplets direct theoretical evidence for a quantitative relati onship between rheology and rheo-optics in blends is provided. To extend th is relationship to a larger window of shear rates, the size dependence of t he scattering has to be taken into account.