Study on the Dynamics of an Antiferroelectric Liquid Crystal by Fluctuation-Induced Kerr Effect

涨落诱导克尔效应反铁电液晶动力学研究

• 批准号: 12650882
• 负责人: ORIHARA Hiroshi
• 金额: $ 2.18万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650882/
• 关键词: antifp.rmelectric; sub phases; fluctuation; nhasp. Transition; electrooptic effect; Kerr effect; nonlinear dielectric permittivity; Soft mode; 非線型誘電率

Several novel intermediate phases, so-called SmC_a^* phase and some femelectnc phases, have been found in chiral smectic liquid crystals in addition to the antiferroelectric SmC_A^* phase. Among them, SmC_a^* phase has been attracting much attention because of its unique physical properties. We have performed Kerr effect and nonlinear dielectric spectroscopy to study the dynamic properties near the SmA-SmC_a^* phase transition point of an antiferroelectric liquid crystal 4-(l-methylheptyloxycarbonyl)phenyl 4-octylcarbonyloxybiphenil-4-carboxylate (MHPOCBC). A Landau-type theory was developed in order to analyze the experimentally obtained frequency dispersions. From the experimental and theoretical results we have successfully obtained the temperature dependence of the relaxation frequency of the soft mode both in the SmA and SmC_a^* phases, which gave the direct evidence that the transition is brought'about by the soft mode condensation. Furthermore, from the slopes of the relaxation frequencies of the soft mode (the amplitude mode) and the ferroelectric mode we could conclude directly that the phase transition is close to a tricritical point, and the discrete model, in which the transitions to tilted phases from the SmA phase take place in each layer even without interactions between neighboring layers, is valid.

除了反铁电 SmC_A^* 相之外，在手性近晶液晶中还发现了几种新颖的中间相，即所谓的 SmC_a^* 相和一些 Femelectnc 相。其中，SmC_a^*相因其独特的物理性质而备受关注。我们利用克尔效应和非线性介电谱研究了反铁电液晶4-(l-甲基庚氧基羰基)苯基4-辛基羰氧基联苯-4-羧酸酯(MHPOCBC)在SmA-SmC_a^*相变点附近的动态特性。朗道型理论的发展是为了分析实验获得的频率色散。根据实验和理论结果，我们成功地获得了SmA和SmC_a^*相中软模弛豫频率的温度依赖性，这直接证明了转变是由软模凝聚引起的。此外，从软模式（振幅模式）和铁电模式的弛豫频率的斜率我们可以直接得出结论，相变接近三临界点，并且离散模型中，从即使相邻层之间没有相互作用，SmA 阶段也会发生在每一层中，也是有效的。

项目成果

V.Bourny and H.Orihara: "Field-induced behaviors near the smectic-A-smectic-C_α^* phase tranition of an antiferroclectric liquid crystal"Phys.Rev.E. 63・2. (2001)

V.Bourny 和 H.Orihara：“反铁电液晶的近晶-A-近晶-C_α^* 相变附近的场诱导行为”Phys.Rev.E（2001）。

V.Bourny et al.: "Observation of the Soft Mode in the Sm-C_α^*Phase"Phys.Rev.E. 62・5. R5903-R5906 (2000)

V.Bourny 等：“Sm-C_α^*相中软模式的观察”Phys.Rev.E. 62・5（2000）。

A.Fajar et al.: "Fluctuation-induced Kerr effect near thesmectic-A-smectic-C_α^* phase tranition"Molecular Crystals and Liquid Crystals.

A. Fajar 等人：“近晶-A-近晶-C_α^* 相变附近波动引起的克尔效应”分子晶体和液晶。

A.Fajar et al.: "Fluctuation-induced Kerr effect near the smectic-A-smectic-C_α* phase transition"Mol. Cryst. Liq. Cryst. Sci. Tech., Sect. A. 366. 653-660 (2001)

A. Fajar 等：“近晶-A-近晶-C_α* 相变引起的波动”，Cryst. Sci.，A. 366. 653-660。 ）

H.Orihara, A.Fajar, V.Bourny: "Observation of soft mode condensation in the SmA-SmC_α^* phase transition by nonlinear dielectric spectroscopy"Phys.Rev.E Rapid Comunications. (in press). (2002)

H.Orihara、A.Fajar、V.Bourny：“通过非线性介电光谱观察 SmA-SmC_α^* 相变中的软模式凝聚”Phys.Rev.E 快速通信（2002 年出版）。