LAUSR

Abstract We report the influence of a very small concentration (0.1 wt%) of ZnO nanoparticles (NPs) on the dielectric and electro-optic properties of a single component ferroelectric liquid crystal in the vicinity of the rarely observed transition between two tilted hexatic phases, hexatic I* and hexatic F*. Despite the small content, NPs brings out substantial difference in the magnitude of the dielectric relaxation frequency associated with softening of the optic mode. The temperature dependence of this frequency has similar behavior in the pure compound as well as for the nanocomposite. In both cases, the thermal behavior is well described by the tilt-bond coupling coefficient that forms the basis of the theoretical model proposed earlier. The tilt angle obtained through two different probes shows a marked difference: While data obtained from X-ray diffraction measurements shows a continuous variation across the hexatic I*-hexatic F* transition, those from electro-optic technique exhibit a drop across the HexI*-HexF* transition, with the extent of decrease being higher for the nanocomposite. Spontaneous polarization studies show clear coexistence of contributions from both the phases. In the light of the fact that the enthalpy change for the transition is very small, the electrooptic studies are shown to be better suited to identify the nature of the transition. The softening feature observed for the relaxation frequency is also seen for two other dynamic quantities, viz., rotational viscosity and switching time. Addition of NPs reduces rotational viscosity causing faster response of the system.