ABSTRACT

We present a theoretical study of the orientational and electrical behaviors of a cholesteric liquid crystal dispersed with ferroelectric nanoparticles. We assume a soft planar coupling between the liquid crystal molecules and the nanoparticles. We consider two spiral structures in the ferroelectric nano-dispersed system under an external electric field. This assumption is due to the fact that the director and the polarization vector would have different pitches of spiral structure. We study the behavior of the average polarization and the pitch of the helical structure as a function of the field strength. The impact of ferroelectric nanoparticles on cholesteric-nematic phase transition is investigated by calculating the critical electric field. The influence of field strength and material parameters on the phase transition is also discussed. The calculations are based on a developed continuum theory and a modified form of free energy for the helical supramolecular structure. The influence of nanoparticle volume fraction on the helix unwinding of both spiral structures is studied. It is found that an electric field with a sufficiently high strength causes an increase in the pitch of the helical structure of polarization. We obtain a critical volume fraction of nanoparticles, after which the pitch of the polarization helical structure differs from the director pitch.

摘要

我们对分散有铁电纳米颗粒的胆甾型液晶的取向和电行为进行了理论研究。我们假设液晶分子和纳米粒子之间存在软平面耦合。我们考虑外部电场下铁电纳米分散系统中的两种螺旋结构。这种假设是由于指向矢和偏振矢量具有不同螺距的螺旋结构。我们研究平均极化和螺旋结构螺距随场强变化的行为。通过计算临界电场研究铁电纳米粒子对胆甾相-向列相变的影响。还讨论了场强和材料参数对相变的影响。计算基于先进的连续介质理论和螺旋超分子结构自由能的修改形式。研究了纳米颗粒体积分数对两种螺旋结构的螺旋展开的影响。研究发现，具有足够高强度的电场会导致极化螺旋结构的螺距增加。我们获得了纳米颗粒的临界体积分数，之后偏振螺旋结构的螺距不同于指向矢螺距。研究发现，具有足够高强度的电场会导致极化螺旋结构的螺距增加。我们获得了纳米颗粒的临界体积分数，之后偏振螺旋结构的螺距不同于指向矢螺距。研究发现，具有足够高强度的电场会导致极化螺旋结构的螺距增加。我们获得了纳米颗粒的临界体积分数，之后偏振螺旋结构的螺距不同于指向矢螺距。