Excluded Volume and Electrostatic Interactions in Liquid Crystals

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This project employs iterative synthetic chemistry in combination with physicochemical characterization (emphasizing nuclear magnetic resonance) to target novel liquid crystal phase symmetries, e.g., biaxial and polar nematic phases, with a goal of delineating the underlying molecular physics. Additionally, the new molecular structures created in this project may point to Liquid Crystal Display (LCD) materials that exhibit more facile electro-optic switching. While the research focus herein is on liquid crystals, these anisotropic fluids may be viewed more generally as an entre to better comprehension of subtle intermolecular interactions in ordinary liquids. Undergraduates (with summer research support) and graduate students are exposed to rigorous training in contemporary synthesis and physical chemistry. Moreover the subject matter is intriguing as well as applicable, and the training enables graduates to pursue a career in the important area of display technologies. Structure-property relations in liquid crystals continue to be a very fertile area for understanding fundamental interactions in soft materials and their associated applications such as Liquid Crystal Displays (LCD)s. In liquids molecular shape considerations-excluded volume interactions-dominate the dynamic, short-range packing, and in some fluids these interactions propagate over mesoscopic scales giving rise to long-range orientational order-the signature of thermotropic liquid crystals. But electrostatic interactions are responsible for condensed phases generally. And in fact, it is the delicate combination of both repulsive and attractive interactions that enable molecules with extreme shapes (rod-like and disc-like) to assemble into a variety of fluid architectures: uniaxial nematics, stratified smectics, columnar discotic phases, and the recently-discovered "banana phases" exhibited by nonlinear molecules. An explosion of Liquid Crystal Displays (LCD)s-a glass "sandwich" whose pixels encapsulate a curious state of matter-has transformed both the desktop and the battlefield in the last decade. LCDs have made images accessible in all areas of science, technology, medicine, government, commerce, and entertainment. Remote imaging makes graphical tracking of severe weather immediately available. It gives physicians an opportunity to "see" patients and monitor intricate medical procedures. Low-cost LCDs make the web accessible in undeveloped countries and LC projectors are essential to high-tech teaching and corporate communications. Chances are that you are reading an electronic version of this abstract on a LCD! We are researching the essential component of these displays, liquid crystal molecules that show electric-field-activated optical properties. Our ultimate goal is to enable a new generation of physical scientists to design new liquid crystals that will continue what the first generation of LCDs did for watches, computers, and cell phones. We anticipate that the new molecules created in our program will lead to more robust LCD materials which in turn, exhibit faster electro-optic switching. In our program undergraduates, vying for competitive summer research support, and graduate students in chemistry and material science are exposed to rigorous training in synthetic and physical chemistry in a subject that is intriguing as well as applicable. The training is designed to enable graduates to pursue a career in the technologically important area of electro-optic displays.