1988 Fiscal Year Final Research Report Summary
Molecular Theoretical Studies on Surface Tension and Molecular Orientation in Liquid Crystals
| Project/Area Number |
61550012
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials
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| Research Institution | Nagoya University |
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Principal Investigator |
HATSUO KIMURA School of Engineering,Nagoya University,Professor, 工学部, 教授 (60023032)
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| Project Period (FY) |
1986 – 1988
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| Keywords | Surface tension / Molecular orientation at interface / Molecular theory of liquid crystals / Intermolecular forces / Nematic-isotropic interface / スメクチック液晶 / ネマチック一等方相界面 / 平滑面固体基板壁 |
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| Research Abstract |
The surface tensions of the nematic liquid crystal are calculated molecular theoratically in mean field approximation at (a)the free surface, (b)the nematic-isotropic (N-I) interface, and (c)the wall of a hard flat material. The liquid crystal is assumed to be the system of hard rod-like molecules.The results express the surface tensions as functions of the nematic director and the molecular orientational order parameter,and each expression consists of respective contributions from (1) the attractive intermolecular force and (2) the excluded volume effect due to the hard core repulsions. It is found that the excluded volume effect favours the normal alignment of molecules at the free surface, While it favours the planar orientation at the N-I interface and on the hard flat wall.
On the other hand,the attractive force,depending on the coupling constants for each molecule,favours one of the normal,tilted and planar orientations irrespective of the kind of interface. On the basis of the theory, many experiments such as the followings are analysed and consistently explained as interplay of the repulsive and attractive forces. (1) Many kind of nematic molecules orient normally at the free surface and planarly on hard walls, (2) the orientation of MBBA and EBBA molecules at the free surface changes continuously from normal to tilted wten the temperature is decreased, (3) the molecular orientation of 70CB and of mixtures of 8CD and 80CB on hard flat wall changes from planar to normal likely as the first order phase transition with the decrease of temperature.
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