Characterization of Nematic Phase of Banana Liquid Crystal
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We report the first detailed optical and electrical characterizations of the nematic (N) phase of a banana liquid crystal, i.e., pretilt angle, and optical and dielectric anisotropies, and point out the difference from those of rodlike molecules. The pretilt angle measurements using a conventional crystal rotation method show that the pretilt angle is very small (less than 1°) even in cells with a polyimide film yielding a high pretilt angle like 8° for calamitic molecules. We also measured the birefringence $\Delta n$ in the N phase as a function of temperature and estimated the orientational order parameter $S$. The medium shows a small negative dielectric anisotropy in the N phase and the anisotropy becomes large in the B2 phase mainly because of the tilt of the molecules from the layer normal.
- Jpn J Appl Phys
Jpn J Appl Phys 45(37), L1013-L1015, 2006-10-25
INSTITUTE OF PURE AND APPLIED PHYSICS