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 -

基本信息

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

项目摘要

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临界场开始通过垂直于对齐方向的电场或磁场（Frederiks Transition）来确定重新定位的。但是，对于确定弹性常数<k_（11）>和<k_（33）>的扭曲弹性常数<k_（22）>，无法使用弹性和<k_（33）>。本研究的第一个目的是通过强制瑞利散射来构建用于确定<k_（22）>的系统。为此，我们通过扩展近晶型A和骨膜B相的扩散测量的强迫瑞利散射系统本身，并通过研究信号强度的温度依赖性。我们还构建了磁场中强迫雷利散射的系统。通过使用标准材料5CB证实，tensi中衍射的松弛时间……从瞬态光栅开始在临界场强度下开始改变。这一事实意味着由于磁场引起的重新定向而导致的扩散常数变化。弹性常数<k_（22）>由临界场确定。获得的结果与其他技术的最新结果一致。为了完成本研究的最终目的，即观察到关键现象，我们对8CB进行了初步测量。尽管尚未完成定量测量值，例如临界指数等定量测量值，但在1度的温度范围内观察到<k_（22）>的增加。由于定量测量的难度是由于温度控制较差，因此正在考虑改进。尽管尚未达到本工作的最终目标，但现在可以轻松地执行<k_（22）>测量值是一个有价值的结果。较少的