Phase Transitions of Liquid Crystal System Consisted by V-Shaped Molecules with Dipole Moments

BAI Lin-yu; LIU Hong

doi:10.3788/YJYXS20132805.0661

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Phase Transitions of Liquid Crystal System Consisted by V-Shaped Molecules with Dipole Moments

Material Physics & Chemistry | 更新时间：2020-08-12

- Phase Transitions of Liquid Crystal System Consisted by V-Shaped Molecules with Dipole Moments
- Chinese Journal of Liquid Crystals and Displays Vol. 28, Issue 5, Pages: 661-667(2013)
- 作者机构：
  
  南京师范大学物理科学与技术学院,江苏南京,210023
- 作者简介：
- 基金信息：
- DOI：10.3788/YJYXS20132805.0661
  CLC： O753+.2
- Received：14 May 2013，
  
  Revised：13 June 2013，
  
  Published：15 October 2013
- 稿件说明：
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白林玉, 刘红. 含偶极矩的V形液晶分子系统的相变[J]. 液晶与显示, 2013,28(5): 661-667

BAI Lin-yu, LIU Hong. Phase Transitions of Liquid Crystal System Consisted by V-Shaped Molecules with Dipole Moments[J]. , 2013,28(5): 661-667
白林玉, 刘红. 含偶极矩的V形液晶分子系统的相变[J]. 液晶与显示, 2013,28(5): 661-667 DOI： 10.3788/YJYXS20132805.0661.

BAI Lin-yu, LIU Hong. Phase Transitions of Liquid Crystal System Consisted by V-Shaped Molecules with Dipole Moments[J]. , 2013,28(5): 661-667 DOI： 10.3788/YJYXS20132805.0661.

摘要

文章中考虑了一带有电偶极矩的V形液晶分子系统

假设液晶分子长棒间的简单相互作用以及电偶极矩间的相互作用形式

利用平均场理论

得到含电偶极矩的V形液晶分子系统在电偶极矩间相互作用强度(

)和温度(

)平面内的相图

以及在V形液晶分子间夹角(

)和温度平面内的三类相图。结果表明

在

平面内的相图曲线中

存在由各向同性相经一级相变直接进入双轴向列相的Landau曲线;而在

-t平面内的第一类相图曲线中

当

较小时

不存在Landau曲线;在第二类相图中(

较大时)

在合适的电偶极矩相互作用强度和分子间夹角的范围内

系统的相变曲线中才会出现Landau曲线;在第三类相图中(

最大时)

相图特征则与第二类相图相反。

Abstract

The phase transitions of liquid crystal system consisted by V-shaped molecules with dipole moments are studied in this paper. Based on a simple interaction energy between rigid molecules and interaction energy between dipoles

the phase diagrams in the plane of interaction strength between dipoles (

) and temperature (

) are obtained by mean-field theory. Three types of phase diagrams in the plane of the angle (

) of the V-shaped molecules and temperature are also obtained. The results show that in the

plane

decreasing temperature can make the isotropic phase entering into biaxial nematic phase by the first order transition

therefore Landau curve exists. In the

-t

plane

the first type of phase diagram shows that

while

is relatively small

Landau curve does not exist. Yet

in the second type of phase diagram

where

is larger

only for appropriate interaction strength and in the appropriate range of values

can Landau curve exist. In the third type where

is the largest

the feature of the phase diagram is the opposite of the feature of the second type.

关键词

Keywords

references

Freiser M J. Ordered states of a nematic liquid [J]. Phys. Rev. Lett., 1970, 24(19):1041-1043.[2] Yu L J, Saupe A. Observation of a biaxial nematic phase in potassium laurate-1-decanol-water mixtures [J]. Phys. Rev. Lett., 1980, 45(12):1000-1003.[3] Shenouda I G, Shi Y,Neubert M E. Mesomorphic properties of 4-[3',4',5'-tri(p-n-Dodecyloxybenzyloxy)]-benzoyloxy-4'''-p-n-Dodecyloxybenzyloxybiphenyl [J]. Mol.Cryst.Liq.Cryst., 1994,257(1):209-218.[4] Hughes J R, Kothe G, Luckhurst G R, et al. A deuterium nuclear magnetic resonance investigation of the symmetry and orientational order of the nematic phase of 4-[3,4,5-tris(4-dodecyloxybenzyloxy)benzoyloxy]-4'-(4-dodecyloxybenzoyloxy)-1,1'-biphenyl. A biaxial nematic? [J]. J. Chem. Phys., 1997,107(21):9252-9263.[5] Acharya B R, Primak A, Kumar S. Biaxial nematic phase in bent-core thermotropic mesogens [J]. Phys. Rev. Lett., 2004, 92(14):145506(1-4).[6] Madsen L A, Dingemans T J, Nakata M, et al. Thermotropic biaxial nematic liquid crystals [J]. Phys. Rev. Lett., 2004,92(14):145505-(1-4).[7] Neupane K,Kang S W,Sharma S, et al. Dynamic light scattering study of biaxial ordering in a ermotropic liquid crystal [J]. Phys. Rev. Lett., 2006, 97(20):207802(1-4).[8] Bates M A, Luckhurst G R. Biaxial nematic phases and V-shaped molecules:A monte carlo simulation study [J]. Phys. Rev. E, 2005, 72(5):051702(1-15).[9] 王慧. 对称Y型分子向列相液晶的相变 [J]. 液晶与显示, 2011, 26(3):301-305.[10] Bates M A. Bent core molecules and the biaxial nematic phase:A transverse dipole widens the optimal angle [J]. Chem. Phys. Lett., 2007,437(4-6):189-192.[11] Vertogen G,Flapper S D P, Dullemond O. Elastic constants of nermatic and cholesteric liquid crystals and tensor fields [J]. J. Chem. Phys. 1982, 76(1):616-618.

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