Amelia M. Lapeña and Rebecca M. Nyquist . This is a collaboration with Stephen. A. Langer and Sharon C. Glotzer at NIST, and Roland Ennis and Peter Palffy-Muhoray at Kent State University.

We are studying the kinetics of phase separation in rod/coil mixtures numerically. This is relevant to polymer-stabilized liquid crystals (PSLC's), used for displays and other optical devices. The key to the effectiveness of PSLC's is the liquid crystal/polymer domain morphology. The polymer-rich domains form a fibrillar network with a large surface area that tends to stabilize liquid crystal order efficiently even at low polymer concentrations. Here is an experimental scanning electron micrograph image of a PSLC system by Deng-Ke Yang and coworkers at the Liquid Crystal Institute at Kent State University.

D. K. Yang, L. C. Chien, Y. K. Fung, in Liquid crystals in complex geometries formed by polymer and porous networks, ed. G. P. Crawford and S. Zumer (Taylor & Francis, London, 1996). The strands are polymer rich domains that have formed by polymerization of monomers initially mixed with a nematic liquid crystal. The strands run in the direction of the nematic order in the liquid crystal matrix. This network morphology arises from the interplay of several different nonequilibrium processes. The materials are typically made by photopolymerization of monomers dissolved in an ordered phase of the liquid crystal (typically nematic or cholesteric). As the polymerization proceeds, the polymer tends to separate from the liquid crystal, forming an isotropic phase rich in polymers coexisting with an ordered phase rich in liquid crystals. A theoretical description of this process must therefore contain the kinetics of polymerization, phase separation and phase ordering. Our aim is to develop guidelines for the rational tailoring and design of nonequilibrium morphologies.

Related Publications:

A. J. Liu, Liq. Cryst. Today (to appear). "Morphology development in liquid-crystal/polymer mixtures."

A. J. Liu and G. H. Fredrickson, Macromolecules 29, 8000 (1996). "Phase separation kinetics of rod/coil mixtures."

S. K. Lee, A. O. Oertli, M. Gannon, A. J. Liu, D. S. Pearson, H.-W. Schmidt and G. H. Fredrickson, Macromolecules 27, 3955 (1994). "Phase behavior of liquid crystalline polymer/model compound mixtures: theory and experiment."

A. J. Liu and G. H. Fredrickson, Macromolecules 26, 2817 (1993). "Free energy functionals for liquid crystalline polymer solutions and blends."