Polymeric Bicontinuous Microemulsions

A polymeric bicontinuous microemulsion (BmE) contains interpenetrating domains with dimensions ranging from 10 nanometers to 1 micron created by blending appropriate amounts of two incompatible homopolymers with the corresponding diblock copolymer. Previous experiments have identified the BmE in a narrow channel of compositions that separates regions of lamellar (LAM) order and macroscopic phase separation, associated with the weak first-order Brazaovskii and Ising universality classes, respectively. We have explored the phase behavior of a model ternary system comprised of poly(cyclohexylethylene) (PCHE), poly(ethylene) (PE) and the associated PCHE-PE diblock copolymer. Small-angle x-ray scattering, transmission electron microscopy, and optical transmission experiments have precisely located the line of congruent transitions that defines the peak temperature separating the lamellar and disordered states and terminates at the BmE. These results will be discussed in the context of the roles of fluctuation effects and conformational asymmetry in defining interfacial curvature and the structure of the phase prism.
* Research conducted in collaboration with Robert Hickey, Timothy Gillard, Matthew Irwin, David Morse, and Timothy Lodge.