Cyanobiphenyl liquid crystal composites with gold nanoparticles

Abstract

We study composites of mainly room temperature nematic cyanobiphenyl liquid crystals (nCB with n = 5, 6, 7, and 8) with gold nanoparticles (GNP). We report that doped GNP dramatically affects the material and, consequently, display parameters and mesophase stability of 5CB, 6CB, and 7CB homologues, while no homogeneous dispersion of GNP occurs in the 8CB homologue. We report several composites with values of switching voltages and times a few times lower than those for pure nematics, and with a broader operational thermal range, which makes them good candidates for application in liquid crystal (LC) display devices. We show that the amount of carbon atoms n in the alkyl "tail" of CB's constituent molecules and the concentration of doped GNP are critical factors in the behavior of the material parameters in the nanocomposites. We report certain correlations of the behavior of the material parameters with odd-to-even-to-odd changes in n. We propose that the doped nanoparticles aggregate with LC molecules affecting the local ordering, and consequently changing nCB's material parameters. The study of the morphology of the samples by SEM and AFM imaging techniques articulates our proposed ideas.