Experimental evidence of continuous isotropic-nematic phase transition in CdS nanowire nanocomposites of a nematic liquid crystal

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.