2003 Fiscal Year Final Research Report Summary
Liquid Crystalline Ordering in Very Thin System
| Project/Area Number |
14540355
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
物性一般(含基礎論)
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| Research Institution | Mie University |
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Principal Investigator |
YAMASHITA Mamoru Mie University, Faculty of Engineering, Professor, 工学部, 教授 (20249600)
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| Project Period (FY) |
2002 – 2003
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| Keywords | nematic phase / Maier-Saupe model / symmetry breaking potential / phase diagram / freely suspended film / ferroelectric liquid crystals / thin liquid crystal cell / unstable state |
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| Research Abstract |
The orders of liquid crystals are generally soft, and are affected by the boundary conditions. For the system of very thin width, we see the phase change which differs from the one at the bulk system. Due to the inhomogeneity at the walls, the ordering of liquid crystal becomes inhomogeneous. In the present investigation, the inhomogeneity due to wall is described in terms of the fictitious field, and the method to elucidate the phase transitions of the thin system by analyzing the field on the phase diagram of the corresponding bulk system is introduced. On the basis of this theory, the orderings in the very thin nematics and the freely suspended film of ferroelectric smectics are studied.
In case the boundary enhances the ordering, the fictitious field is positive, and for the system whose transition is of the second order at the bulk, no phase transition occurs because the singularity is restricted to the zero-field region. In this respect we study the systems whose transitions are of the first order. The ferroelectric smectic phase of material C7 together with the nematic system exhibits the first order phase transition, and both of the systems with very small thickness are studied here.
The phase diagram of the nematics is proved to be same topologically to the three-state Potts model, and on the basis of this phase diagram the phase changes under various anchoring conditions are classified. The case of homeotropic anchoring condition is studied in detail, in which unstable phase which never appear in the bulk is shown to appear in the thin system. The freely suspended film of C7 is proved to show the similar unstable phase. For smectics the field versus temperature phase diagram is obtained and general feature of the phase change due to the wall is clarified.
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