Guest-host interaction of some chloroanthraquinone dyes doped in liquid crystalline matrix and effect of addition of carbon nanotube

Abstract

Liquid crystals (LCs) are commonly used in displays. For practical guest-host applications, it is important to choose dyes with a high ability of orientation in the liquid crystal matrix. In this work, two different nematic liquid crystals (E7 and ZLI-1132) were separately doped (1% m/m) with four different dyes (1-chloro, 2-chloro, 1,5-dichloro and 1,8-dichloro anthraquinone). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, carbon nanotubes (CNTs) were added (0.05% m/m) to these solutions and the same parameters except solubilities were studied again. Although the solubilities of dyes in the liquid crystal ZLI-1132 were lower than those of E7, the order parameters were much higher. Addition of carbon nanotubes as dopant resulted in an increase in order parameter. Nematic/isotropic microphase separation in doped liquid crystal samples was detected by polarised microscopy. Determination of both phase transition temperatures and phase type was done by temperature dependent texture investigations between crossed polarisers. The dyes and CNTs did not significantly destabilise the mesomorphic phase of nematic hosts. When passing a phase transition, characteristic textures and structures changed with the temperature increasing and decreasing. The nematic-isotropic transition occurred in several pictures (textures). An appreciable change in textures was not observed with the addition of dopant(s) when compared with pure liquid crystal textures. © 2013 Elsevier B.V.