Pre-transitional Phenomenon of Nematic-smectic Phase Transition Observed by Elastic Constant - Observation of Frederiks Transition by Forced Rayleigh Scattering -

通过弹性常数观察到的向列-近晶相变的预转变现象 - 通过受迫瑞利散射观察 Frederiks 相变 -

• 批准号: 60540199
• 负责人: TAKEZOE Hideo
• 金额: $ 1.02万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60540199/
• 关键词: Liquid Crystal; Twist Elastic Constant; Forced Rayleigh Scattering; Frederiks Transition; Pre-transitional Phenomenon; Critical Magnetic Field; 臨界現象

The elastic constants of liquid crystals are usually determined by detecting the critical field where the reorientation starts to occur by applying an electric or a magnetic field (Frederiks transition) perpendicular to the alignment direction. As for the twist elastic constant <K_(22)> , however, usual methods for determining the elastic constants <K_(11)> and <K_(33)> for splay and bend deformations can not be used. The first purpose of the present study was to construct the system for determining <K_(22)> by means of forced Rayleigh scattering.For this purpose, we examined and improved our forced Rayleigh scattering system itself by extending the diffusion measurements in nematics to in smectic A and smectic B phases and by investigating the temperature dependence of the signal intensity. We have also constructed the system of the forced Rayleigh scattering in a magnetic field. It was confirmed by using the standard material, 5CB, that the relaxation time of the diffraction in tensi … More ty from the transient grating starts to change at the critical field strength. This fact means that the diffusion constant changes due to the magnetic field induced reorientation. The elastic constant <K_(22)> was determined by the critical field. The results obtained agreed with the recent results by other techniques.To accomplish the final purpose of the present study, i.e., observation of the critical phenomenon, we carried out the preliminary measurements on 8CB. The increase of <K_(22)> was observed within the temperature range of 1 degree from the nematicsmectic A phase transition temperature, although the quantitative measurements such as the critical exponent have not been done. Since the difficulty of the quantitative measurements is due to the poor temperature control, the improvement is now under consideration. Thus it is a valuable result that the <K_(22)> measurements is now easily performed by forced Rayleigh scattering, although the final goal of the present work has not been reached. Less

液晶的弹性常数通常是通过检测与取向方向垂直的电场或磁场(Frederks转变)开始发生重定向的临界场来确定的。至于扭转弹性常数&lt；K_(22)&gt；则不能用通常的方法确定张开和弯曲变形的弹性常数&lt；K_(11)&gt；和&lt；K_(33)&gt；。本研究的第一个目的是建立强迫瑞利散射测量系统，通过将向列相的扩散测量扩展到近晶A相和近晶B相，并研究信号强度的温度依赖性，对我们的强迫瑞利散射系统本身进行了检验和改进。我们还构造了磁场中的强迫瑞利散射系统。用标准物质5CB证实了TenSi…的衍射弛豫时间在临界场强处，更多的来自暂态光栅的Ty开始发生变化。这意味着，由于磁场诱导的重取向，扩散常数发生了变化。弹性常数&lt；K_(22)&gt；由临界场确定。为了达到本研究的最终目的，即观察临界现象，我们对8CB进行了初步测量。在距向列相A相变温度1℃的温度范围内，观察到了~lt；K_(22)&Gt；的增加，但尚未进行临界指数等定量测量。由于温度控制不佳造成了定量测量的困难，目前正在考虑改进。因此，这是一个有价值的结果，现在可以很容易地通过强迫瑞利散射来进行&lt；K(22)&gt；测量，尽管本工作的最终目标还没有达到。较少

项目成果

M. Hara, H. Takezoe and A. Fukuda: "Forced Rayleigh Scattering in n'CBs (n=5-9) with Methyl Red and Binary Mass Diffusion Constants" Jpn. J. Appl. Phys.25. 1756-1761 (1986)

M. Hara、H. Takezoe 和 A. Fukuda：“具有甲基红和二元质量扩散常数的 nCB（n=5-9）中的强制瑞利散射”Jpn。

M.Hara: Jpn.J.Appl.Phys.24. L777-L780 (1985)

M.Hara：Jpn.J.Appl.Phys.24。

M. Hara, H. Tenmei, S. Ichikawa, H. Takezoe and A. Fukuda: "Anisotropy of Binary Mass Diffusion Constants in Nematic, Smectic A and Smectic B Phases Studied by Forced Rayleigh Scattering" Jpn. J. Appl. Phys.24. L777-L780 (1985)

M. Hara、H. Tenmei、S. Ichikawa、H. Takezoe 和 A. Fukuda：“通过强制瑞利散射研究的向列相、近晶 A 相和近晶 B 相中二元质量扩散常数的各向异性”Jpn。

H. Takezoe, T. Toyooka, J. Hirakata and A. Fukuda: "Determination of Twist Elastic Constant <K_(22)> by Forced Rayleigh Scattering" Jpn. J. Appl. Phys.26. (1987)

H. Takezoe、T. Toyooka、J. Hirakata 和 A. Fukuda：“通过强制瑞利散射测定扭曲弹性常数 <K_(22)>” Jpn。

M.Hara: Jpn.J.Appl.Phys.25. 1756-1761 (1986)

M.Hara：Jpn.J.Appl.Phys.25。