ABSTRACT

The calamitic nematic liquid crystal generally exhibits a discontinuous weakly first-order isotropic-nematic (I-N) phase transition. We found that, on the incorporation of CdS nanowire in the nematic host, the weakly first-order discontinuous I-N phase transition evolved as a continuous phase transition. The parallel and perpendicular components of dielectric permittivity and bulk conductivity of nanocomposites of CdS nanowires of a nematic liquid crystal (NLC) are found to follow continuous I-N phase transition in contrast to the discontinuous weakly first-order transition of the pure host nematic liquid crystal. This was further confirmed from scattered iGntensity measurements on the CdS nanocomposite samples of nematic liquid crystal in homeotropically aligned cells. Such measurements indicate a continuous phase transition for the nanocomposites of NLC having concentrations less than 0.2 wt% of CdS nanowires in NLC. The dielectric anisotropy, birefringence, threshold voltage of nanocomposites of CdS nanowire in a calamitic nematic liquid crystal with varying concentration of the nanowire have been measured. The ionic conductivity of nanocomposites of CdS nanowires of NLC increases with increasing concentration of CdS nanowires.

摘要

棒状向列液晶通常表现出不连续的弱一级各向同性-向列 (IN) 相变。我们发现，在向列基质中加入 CdS 纳米线后，弱一阶不连续 IN 相变演变为连续相变。发现向列液晶 (NLC) 的 CdS 纳米线纳米复合材料的介电常数和体电导率的平行和垂直分量遵循连续的 IN 相变，这与纯主体向列液晶的不连续弱一级转变相反。这通过对垂直排列单元中向列液晶的 CdS 纳米复合材料样品的散射 iGntensity 测量得到进一步证实。这样的测量表明在 NLC 中 CdS 纳米线浓度小于 0.2 重量％的 NLC 纳米复合材料的连续相变。已经测量了具有不同纳米线浓度的棒状向列液晶中 CdS 纳米线的纳米复合材料的介电各向异性、双折射、阈值电压。NLC的CdS纳米线纳米复合材料的离子电导率随着CdS纳米线浓度的增加而增加。