DESIGN OF BICONTINUOUS POLYMERIC MICROEMULSIONS

Recent experiments suggest that thermodynamically stable, bicontinuous microemulsions can be achieved in symmetric ternary blends of two hom opolymers and a diblock copolymer by formulating alloys with compositi ons near mean-field isotropic Lifshitz points. We argue that practical application of this design criterion may require use of homopolymers of unequal molecular weights and block copolymers of different archite cture. We demonstrate the existence of, and explicitly locate, mean-fi eld isotropic Lifshitz points in ternary blends with homopolymer molec ular weight asymmetry and either AB diblock or ABA triblock copolymer architectures. These calculations considerably expand the parameter sp ace for observing bicontinuous microemulsions and allow for more flexi bility in tailoring melt rheological properties and solid-state mechan ical properties. (C) 1997 John Wiley & Sons, Inc.