Khandelwal, Anjuli and Yadav, Maneesha and Bawa, S. S.
(2008)
Twist grain boundary phases giving developable domain textures as those exhibited by columnar phases.
Molecular Crystals and Liquid Crystals, 489.
298-309 .
ISSN 1563-5287
Abstract
This paper reports experimental observation of TGBA, TGBC* phases in a mixture of Liquid Crystals. The phases exhibit developable domain textures as those observed for columnar systems. Under polarizing microscope they appear as cylindrical and cone-like domain texture. In such domains the smectic blocks, the grain boundaries and the layers of helical structure of TGB phase are coiled in a double twist manner around an axis. A peculiar texture is obtained in the intermediate region between the TGBA and Cholesteric phase while cooling the sample from isotropic phase. This phase is identified as 'Twist Grain Boundary phase of Hexatics' (TGBH) proposed theoretically by Kamien. The phase reappears as TGBA is heated. The Twist grain boundary phase of Hexatics consists of twisted N+6 regions separated by grain boundaries. Within each region the bond order twists with pitch 2 pi/q and the director is aligned in a nematic state. The director is rotated by some finite angle across a grain boundary moving along the pitch axis that is perpendicular to the nematic director.
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