Bistable states and frequency-dependent switching characteristics of the mesophases of a high dipole moment superparaelectric liquid crystal.

The electro-optical (EO) switching properties of a rod-shaped liquid crystal (LC) molecule, WJ-16, which exhibits a molecular dipole moment of 10.8 D and superparaelectric (SPE) behaviour in its nematic and smectic-A (SmA) phases, are investigated. Similar measurements are also performed for the conventional paraelectric LCs, 8CB and 8OCB, and the results for the three LCs are compared to illustrate the differences between the SPE behaviour and the conventional paraelectric EO properties. The switching voltage (V 0.1) required for the molecular reorientation from the planar to homeotropic state is used as the key parameter for these investigations. It is found to be highly frequency dependent for the nematic phase of WJ-16, whereas it remains almost frequency independent for both 8CB and 8OCB. The presence of nanoscale polar clusters in WJ-16 arises from the polarization-splay coupling, and these clusters facilitate the formation of clear bistable states in the SmA phase, as evidenced by a large optical memory effect. However, such effects are not observed in 8CB and 8OCB. The switching characteristics provide a clear distinction between the SPE material and the conventional paraelectric LCs. The observed characteristics indicate the potential of using WJ-16 in optical modulation and memory devices.