Sigarev AA, Vij JK, Panarin YP, Goodby JW
Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland and Department of Molecular Physics and Electronics, Research Institute of Physical Problems, Moscow 103460, Russia.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Aug;62(2 Pt A):2269-78. doi: 10.1103/physreve.62.2269.
IR dichroism and the structure of a homogeneously aligned cell of a chiral smectic antiferroelectric liquid crystal (R)-1-methylheptyl 4-(4(')-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate [with acronym (R)-12OF1M7] in a ferrielectric subphase in the temperature range between the antiferroelectric phase (also referred to as Fi2) and the smectic-C*(SmC*) phase are studied using polarized Fourier transform IR spectroscopy. The polarization dependencies of the absorbance for several characteristic bands are quantitatively analyzed for different stages of the electrically induced structural transformations in the sample, including the helix unwinding and the phase transition from the ferriphase to the SmC* phase. A qualitative similarity of the voltage dependence of the normalized angular shift of the IR absorbance profile for the "chiral" carbonyl band to that of the normalized macroscopic polarization is found. The voltage dependent dichroic properties of the sample are analyzed in terms of the molecular structure and unwinding of the helical structure under an external electric field. The rotational orientational biasing of the carbonyl groups around the long molecular axis is confirmed by the spectral data. The analysis of IR dichroic data for the field induced SmC* phase is used to determine the rotational orientational distributions for the carbonyl groups.
利用偏振傅里叶变换红外光谱研究了手性近晶反铁电液晶（R）-1-甲基庚基4-（4′-十二烷氧基联苯-4-基羰氧基）-3-氟苯甲酸酯[简称为（R）-12OF1M7]在反铁电相（也称为Fi2）和近晶C*（SmC*）相之间温度范围内的铁电亚相中的红外二色性及其均匀排列盒的结构。针对样品中电诱导结构转变的不同阶段，包括螺旋展开以及从铁电相到SmC相的相变，定量分析了几个特征带吸光度的偏振依赖性。发现“手性”羰基带的红外吸收谱归一化角位移的电压依赖性与归一化宏观极化的电压依赖性在性质上具有相似性。根据分子结构和外电场作用下螺旋结构的展开情况，分析了样品的电压依赖性二色性特性。光谱数据证实了羰基围绕分子长轴的旋转取向偏置。利用场诱导SmC相的红外二色性数据分析羰基的旋转取向分布。
