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Antiferroelectricity and Intermolecular Interactions in Chiral Smectic Liquid Crystals

手性近晶液晶中的反铁电性和分子间相互作用

基本信息

批准号：
06102005
负责人：
FUKUDA Atsuo
金额：
$ 121.6万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Specially Promoted Research
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

We have studied antiferroelectricity in liquid crystals from various viewpoints and established the P_X model ; the hindered rotational motion of molecules about their long axs produces spontaneous polarizations parallel to the tilt plane near smectic layr boundaries and stabilizes the antiferroelectric SC_A^<**> phase. Based on the P_X model, we have analyzed the frustration between ferro- and antiferro-electricity, introduced a novel concept, thresholdless antiferroelectricity (TLAF), and explained the V-shaped switching observed in a novel, apparently antiferroelectric liquid crystal mixture and usable in liquid crystal displays (LCDs) with active matrix electrodes. Details are :1) Higher-order X-ray Bragg peaks indicated a correlation between the stable antiferroelectricity and higher smectic-layr order.2) Spectroscopy clarified the following four facts :(1) Polarized Raman confirmed the molecular arrangements in SC^<**> and SC_A^<**>.(2) NMR and polarized IR (PIR) verified the ben … More t structure, the precessional motion and the biaxiality around the average chain axs of chiral alkyl chains in liquid crystal phases.(3) PIR proved the hindrance of molecular rotational motion about their long axs and a difference in the hindered direction between SC^<**> and SC_A^<**>, assigning the threshold of the triastable switching to the barrier between the SC^<**> and SC_A^<**> hindered directions and suggesting the P_X model.(4) PIR verified the chiral alkyl chain precessional motion, and NMR indicted its collective character.3) The optical Kerr effect with 130 fs pump pulses dose not show any critical slowing down, indicating no coupling between the laser-induced molecular reorientation with tau-10^<11>s and the polarization.4) Optical microscope observation of the subphases in free-standing films under temperature gradients supported Yamashita's ANNNI+J_3 model.5) Electro-optical observation of an apparently antiferroelectric liquid crystall mixture showed the V-shaped switching, resulting in the TLAF based on the randomization and Langevin type alignment of director tilting from layr to layr.6) PIR and NMR showed that the P_X model also holds in SI_A^<**>.7) CD spectroscopy proved the dynamical character of the SC_<alpha> helicoidal structure, supporting a speculation of SC_<alpha> characterized by thermally excited C-director disclinations.8) Dimer molecules with chiral units connected with polymethlene chain indicated the importance of dipole-dipole interaction in SC_A^<**>.9) A 5 T superconducting magnet simplified the fabrication of liquid crystal cells, furthering to study the aligning mechanism and the defect structure. Less

我们从不同的角度研究了液晶中的反铁电性，建立了P_X模型；分子围绕其长轴的受阻旋转运动在近晶层边界附近产生平行于倾斜平面的自发极化，并稳定了反铁电SC_A^<**>相。基于P_X模型，我们分析了铁电和反铁电之间的挫败感，引入了一个新的概念，无阈值反铁电（TLAF），并解释了在一种新型的、明显反铁电的液晶混合物中观察到的v形开关，该开关可用于具有有源矩阵电极的液晶显示器（lcd）。详细说明：1)高阶x射线Bragg峰表明稳定的反铁电性与高阶近晶层之间存在相关性。(1)极化拉曼光谱证实了SC^<**>和SC_A^<**>中的分子排列。(2)核磁共振和偏振红外（PIR）验证了液晶相中手性烷基链的结构、旋进运动和围绕平均链轴的双轴性。(3) PIR证明了分子沿长轴旋转运动的阻碍以及SC^<**>和SC_A^<**>之间的阻碍方向的差异，将可稳态切换的阈值指定为SC^<**>和SC_A^<**>之间的阻碍方向，并提出了P_X模型。(4) PIR证实了手性烷基链的旋进运动，NMR证实了其集体性。3) 130 fs泵浦脉冲的光学Kerr效应没有表现出临界慢化，表明在tau-10^<11>s的激光诱导分子重定向与偏振之间没有耦合。4)支持Yamashita的ANNNI+J_3模型的温度梯度下独立薄膜中亚相的光学显微镜观察。5)对明显反铁电的液晶混合物进行电光观察，发现其发生了v型开关，导致基于随机化取向的TLAF层与层之间倾斜。6) PIR和NMR证实了SI_A^<**>的P_X模型也成立。7)CD谱证实了SC_< α >螺旋结构的动力学特征，支持了SC_< α >的热激发c指向偏差表征的推测。8)手性单元与聚甲基链连接的二聚体分子表明了SC_A^<**>中偶极-偶极相互作用的重要性。9)5t超导磁体简化了液晶胞的制作，进一步研究了液晶胞的定向机制和缺陷结构。少