Influence of zinc oxide nanorods on an orientationally ordered fluid comprising soft-bent dimers

Abstract

Bent-core liquid crystals (LCs) introduced a whole new dimension to the science of LCs. Besides re-emphasizing the importance of the shape of the molecule, they brought in phases with symmetry, not known earlier. Another sub-class of systems that is emerging is that of soft-bent molecules. In contrast with the bent-core molecules, here the bend is achieved through the parity of the aliphatic linker that connects two monomers. They hold the unique advantage that a simple variation of temperature can favour different conformer states and thus govern the self-assembled structure. A highlight of the power of this route is seen in terms of the discovery of a new type of nematic, viz., twist-bend nematic. Investigations on not only this phase but also the regular nematic that often precedes it have received significant attention in the last few years. Here we present results on the regular nematic phase of a binary mixture comprising such a soft-bent dimer, known in the literature as CB7CB, by incorporating zinc oxide nanorods (NRs) into the system. The NRs with an aspect ratio of ∼7.2, not very different from that of LCs, further accentuate the importance of shape and shape anisotropy of the entities. Specifically, we observe that the nematic-isotropic transition temperature increases by ∼1.9K even for a low concentration of 4% NRs.While the dielectric anisotropy decreases, birefringence shows a substantial increase, adding to the complexity of the influence. Upon addition of minute amount of NRs (1%), while the splay elastic constant gets enhanced, its bend counterpart not only gets reduced but retains the convex-shaped thermal profile seen for the parent mixture.