Start
Aug 19, 2010 - 16:00
End
Aug 19, 2010 - 17:30
Venue
Creativity Hall (Room No. 118)
Event Type
Speaker
Dr. Sachin Velankar Dept. of Chemical Engineering University of Pittsburgh
Title
Interfacial phenomena and structure control in immiscible polymer blends: Applying insights from oil/water systems.
Abstract: Immiscible homopolymers are often blended together to achieve properties not possible with a single homopolymer. We will describe the effect of interfacial modifiers on the structure and flow properties of polymer blends. We will also discuss attempts to transplant existing strategies of structure control from small-molecule two-phase systems e.g. mayonnaise to immiscible polymer blends. As a first example of interfacial modifiers we will consider block copolymers which are often used to promote blending of immiscible polymers. Experiments show significant rheological consequences due to added diblock copolymer e.g. as little as 0.1 wt.% copolymer can double the blend viscosity. Such large rheological effects are attributable to interfacial immobilization induced by the added copolymer. Interfacial immobilization can also explain why the copolymer can suppress coalescence in some cases. In such cases we can transplant methods of structure control in oil/water emulsions to polymer blends. As a second example of interfacial modifiers we will consider non-amphiphilic particles which adsorb at the interface between immiscible polymers. Once again analogous to research in oil/water systems such particles can stabilize polymer blends and foams. Furthermore anisotropic morphologies can be realized by interfacial “jamming” i.e. tightly covering interfaces with particles so that the interface cannot relax into an isotropic morphology. In summary even small amounts of interfacial modifiers combined with a suitable processing history can effect large changes in the morphology of polymer blends.