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Free-standing films of twist grain boundary TGBA and UTGBC* liquid crystals studied by fluorescence confocal polarizing microscopy
Authors:I I Smalyukh  R Pratibha    N V Madhusudana
Institution:1. Chemical Physics Interdisciplinary Program and Liquid Crystal Institute Kent State University PO Box 5190 Kent OH 44242-0001 USA;2. Raman Research Institute C. V. Raman Avenue Bangalore 560 080 India
Abstract:The director structures, meniscus profile, and defects in free-standing films of the twist grain boundary TGBA and UTGBC* liquid crystals were studied. The films were characterized by a combination of polarizing microscopy and fluorescence confocal polarizing microscopy. Five principal regions of meniscus were distinguished. When film thickness in the meniscus is much smaller then the TGB pitch, there is no difference between the free-standing films of TGB and ordinary smectic A liquid crystals. When the film thickness is larger than the TGB pitch, filamentary texture is observed. The 3D director pattern of the filaments are similar to the ground state director fields of TGBA and UTGBC* liquid crystals. In the intermediate thickness region of the meniscus, when the film thickness and TGB pitch are commensurate, a unique radial pattern is observed. Based on the fluorescence confocal polarizing microscopy studies of the director field, we propose a model for the 3D director structure in this part of the meniscus.
Keywords:
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