SC 740 SEMINAR REVIEW
By Deborah Dent
Characterization of Liquid Crystal and Polymer Dispersions
Joe Whitehead, Jr.
Department of Computer Technology
University of Southern Mississippi
Hattiesburg, Mississippi
Friday, April 3, 1998
Dr. Whitehead presented a talk in which he introduced us to Liquid Crystals and Polymer Dispersed Liquid Crystals (PDLC). Traditional, we have been taught that there are three states of matter: solids, liquids, gas. But due to the work of an Austrian botanist, Friedrich Reinitzer, we have a new phase of matter - the liquid crystal phase. In the traditional phases, molecules have certain tendencies. In the solid state, molecules are highly ordered, positionally and orientationally. In the liquid and gas phase molecules have no positional order or orientational order. The characteristic orientational order of the liquid crystal state is found between the traditional solid and liquid phases. Here they may be in two states: crystal or liquid crystal. Dr. Whitehead presented several examples of the uses of liquid crystal such as the watch.
He next introduced us to PDLCs, which are a relatively new class of materials that hold promise for may applications ranging from switchable windows to projection displays. PDLCs were first invented in 1983 at Kent State University. These materials consist of liquid crystal droplets that are dispersed in a solid polymer backbone. The resulting material is a sort of "Swiss cheese" polymer with liquid crystal droplets filling the holes. PDLCs are typically manufactured in two distinct ways: encapsulation and phase separation. Dr. Whitehead described how the Phase Separation is performed. He stated that the separation can take place in one of three ways:
Dr. Whitehead concluded his presentation by presenting information on a current research effort - PDLCs in microgravity. Microgravity is the condition of near weightlessness that results when an object undergoes free fall or is placed at a very great distance from massive objects like the Earth. Dr. Whitehead is currently involved in investigating the intrinsic phase separation processes of PDLCs in microgravity. This appears to be a very interesting and useful research effort.