Polarizations and Symmetries in Liquid Crystals

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9502825 Rosenblatt The purpose of the proposed work is to investigate symmetry- related behavior of liquid crystals. Specifically, the investigations are designed to increase the understanding of how chirality and symmetry affect liquid crystalline behavior. A variety of phenomena related to ferroelectric and antiferroelectric liquid crystals will be studied including the dynamics of the electroclinic effect, low frequency second harmonic generation in ferroelectric liquid crystals, spatially periodic polarizations, the behavior of the antiferroelectric -"disordered" phase transition, and the antiferroelectric - ferroelectric phase transition. The effects of symmetry-breaking surfaces as they relate to liquid crystalline polarizations will be probed. Related investigations on ferroelectric liquid crystals will also be performed, including studies of ionic adsorption and enantiomeric concentration fluctuations. Finally, a new thrust area involving liquid crystals in confined geometries will be explored, with special attention paid to the role of the large surface-to-volume ratio of the host matrix as it relates to chiral liquid crystals. A battery of experimental tools will be used, including static and dynamic light scattering, dielectric relaxation, magnetic and electric birefringence and other electrooptic measurements, magnetic susceptometry, and Freedericksz techniques. %%% This research is designed to increase the understanding of how chirality and symmetry affect liquid crystalline behavior. Symmetry plays an important role in liquid crystalline behavior. In a smectic C phase composed of chiral molecules, for example, one finds a macroscopic polarization in the plane of the smectic layers. At a symmetry-breaking interface there exists a polarization normal to the surface; if the molecules are chiral, lack inversion symmetry, and are tilted with respect to the interface, an additional component of polarization may reside at and parallel to the interfac e. Chirality may also affect the nature of a phase transition, or introduce entirely new phases such as the blue phases. The proposed research will provide a deeper fundamental understanding of these phenomena, and it may also impact the technological infrastructure as well. Work under the prior grant led to a new display technology; the results of work to be performed under the proposed research have the potential to affect current scientific and technological thinking, and possibly have impact on the display industry as well.