Mixed morphology by the extrusion of phase‐separated blends of a melt‐processed polymer and polymer solution

Abstract

The phase behavior and structure development in immiscible blends of melt-extruded polycaprolactone and a viscous aqueous poly(ethylene oxide) solution were investigated. The coextrusion of an aqueous polymer solution and a molten polymer is a largely unexplored technique and offers exciting potential for creating new materials via the execution of chemical reactions in the aqueous phase. Samples were prepared both with and without a block copolymer acting as a surface-active agent. The resulting morphology was characterized with scanning electron microscopy after the removal of the watersoluble phase. Spheres, rods, fibers, and cocontinuous gyroidal structures were observed, yet the exact phase inversion was not observed, and the changes in the feature shape depended on which component composed the major phase. Significant orientation in the flow direction was observed when the less viscous poly(ethylene oxide) was the major phase, whereas orientation was minimal when polycaprolactone was the major phase. These observations indicate that control of the feature shape and orientation may be accomplished through the control of the viscosity. The spontaneous formation of an outer layer of polycaprolactone in all samples was observed, suggesting that the morphology could be induced by control of the material interaction with the extruder die wall. The inclusion of a diblock copolymer significantly reduced the feature size but did not alter the morphology type.