Shtykov N M, Vij J K, Nguyen H T
Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland.
Phys Rev E Stat Nonlin Soft Matter Phys. 2001 May;63(5 Pt 1):051708. doi: 10.1103/PhysRevE.63.051708. Epub 2001 Apr 25.
The antiferroelectric liquid crystal (AFLC) under investigation possesses different helical smectic phases. The various phases have been identified through a texture under cross-polarizers with a homeotropic alignment of the AFLC. Measurements of the optical rotatory power (ORP) of these phases have elucidated the ability of this method for finding phase transitions between several phases and for investigating the helical structure of the antiferroelectric phases. The optical rotatory power as a function of temperature at a fixed wavelength of light was measured for different phases of the investigated AFLC material. The values of the pitch for some of the phases have been calculated from the ORP data. The results of the ORP rule out the simple "clock" model or a clock model with a long pitch superimposed on to it. The results can be explained only in terms of biaxial models, either Ising-type models or a highly distorted "clock" model. It is also found that in the SmCA phase the sense of the helix in the investigated material is left handed, and is opposite to that observed in the SmC phase. The reversal of the helix from left to right handed occurs during the phase transition from the SmCFI1(SmCgamma) to SmCFI2(AF) phase. This fact also allows for SmCA and AF phases to be distinguished from each other.
所研究的反铁电液晶（AFLC）具有不同的螺旋近晶相。通过在具有AFLC垂直取向的正交偏振器下的织构识别出了各个相。对这些相的旋光本领（ORP）的测量阐明了该方法用于发现几个相之间的相变以及研究反铁电相螺旋结构的能力。在固定波长的光下，针对所研究的AFLC材料的不同相测量了作为温度函数的旋光本领。已根据ORP数据计算出一些相的螺距值。ORP的结果排除了简单的“时钟”模型或叠加有长螺距的时钟模型。结果只能用双轴模型来解释，即伊辛型模型或高度扭曲的“时钟”模型。还发现，在所研究的材料中，在SmCA相中螺旋方向是左旋的，与在SmC相中观察到的相反。在从SmCFI1（SmCγ）到SmCFI2（AF）相的相变过程中，螺旋方向从左旋变为右旋。这一事实也使得SmCA相和AF相能够相互区分。
