Browsing by Author "Wang, Shun"

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Surface-induced ordering effect in one antiferroelectric liquid crystal compound
(2009-03-01)
Pan, LiDong
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Wang, Shun
;
Hsu, C. S.
;
Huang, C. C.
;
應用化學系
Null transmission ellipsometer was employed to study the surface-induced tilt transition of an antiferroelectric liquid crystal compound in the bulk smectic-A (SmA) temperature range. The data of the surface tilt transition can be fitted with an extended mean-field model. These results indicate the transition is near a mean-field tricritical point. The surface layers' tilt directions are found to be in different planes several degrees above the bulk SmA-SmC alpha* transition.
Thickness Dependent Phase Behavior of Antiferroelectric Liquid Crystal Films
(2009-10-30)
Pan, LiDong
;
Wang, Shun
;
Hsu, C. S.
;
Huang, C. C.
;
應用化學系
Free standing films of a liquid crystal compound with simple surface enhanced order were studied. The resultant phase diagram demonstrates that (1) the short helical pitch smectic-C-alpha* phase disappears below a film thickness of 10 layers, and (2) the temperature window of a distorted 4 layer smectic-C-FI2* phase increases dramatically upon decreasing film thickness. The experimental findings were attributed to the reduced dimensionality and enhanced surface effects in thin films. The results of the smectic-C-alpha* phase are consistent with what have been reported for helically ordered magnetic thin films, with a noticeable difference due to the opposite effect of the surface on ordering in the two systems.
Unique pitch evolution in the Smectic-C-alpha(*) phase
(2007-08-17)
Liu, Z. Q.
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McCoy, B. K.
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Wang, S. T.
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Pindak, R.
;
Caliebe, W.
Employing resonant x-ray diffraction, we observed unique pitch evolutions in the smectic-C-alpha* phase in mixtures of two antiferroelectric liquid crystals. Our results show that the pitch in this phase continuously evolves across 4 layers, contradicting a theoretical model that predicts that the smectic-C-FI2* phase intervenes in the smectic-C-alpha* phase. The phase sequences we found can be explained by another model that includes one type of long-range interaction among smectic layers.