Varying the blending protocol to control the morphology of model compatibilized polymer blends

The structure of an oil/water emulsion is known to depend on its preparation method. Here, we test whether the preparation protocol can be used to control the morphology of "model" blends of immiscible polymers compatibilized by a diblock copolymer. Two preparation protocols were tested. In the "double blending" protocol, a droplet-matrix blend was blended with additional drop-phase fluid. As in oil/water emulsions, this yielded a drop-within-drop "double emulsion" morphology. Coalescence suppression due to compatibilizer was found crucial to double emulsion stability. The rheology of the double emulsion was qualitatively similar to that of a simple droplet-matrix blend, but with an effectively higher drop volume fraction. In the "multistep concentration" protocol, the drop phase was added gradually (rather than all-at-once) to the matrix phase. While this protocol can realize a high-dispersed phase emulsion in oil/water systems, in this case, phase inversion occurred when the drop volume fraction exceeded 0.5. (c) 2008 American Institute of Chemical Engineers.