The recent discovery of a ferroelectric response to a switching electric field in nematic phases exhibited by bent-core polar molecules, particularly 1,2,4-oxdiazole derivatives, could lead to new avenues for the development of electro-optic devices. For the first time, we report ferroelectric-like switching under the influence of a triangular wave electric field in the nematic phase exhibited by unsymmetrical achiral four-ring bent-core compounds. These bent-core molecules, exhibiting a large nematic phase range (>70 C), consist of two unequal lengths in two wings and possess a polar moiety at one end and an alkyloxy chain at the other end. An anomalous variation in spontaneous polarization as a function of temperature in the nematic phase is distinctly observed, which is similar to the results reported only in the low temperature region of the nematic phase. Electro-optical, current-response and dielectric studies of aligned samples corroborate earlier reports of the proposed polar structure of the cybotactic clusters and the ferroelectric-like polar switching of these nematic phases.
Here we report the influence of terminal –F, –Cl and –NO2 substitution on the elastic, dielectric and polar switching behavior of four-ring bent-core liquid crystals (LCs).
We have investigated two new series of unsymmetrical four-ring bent-core molecules with methylated azobenzene wings exhibiting nematic mesophase. The difference between the two series was in the relative position of the methyl (−CH 3 ) substituent with respect to the azo (−NN−) linkage in the molecule. Single-crystal X-ray diffraction analysis unravels significant insights into the spatial molecular arrangement and molecular stacking interactions of these bent-core systems. The materials were able to show photoswitching behavior and photomasking effect in the liquid-crystalline state via nematic to isotropic (order to disorder) transition when illuminated with UV light. In solid state, the materials exhibit photochromism upon UV light exposure. One of the representative compounds (2/12) was studied to observe the optically enhanced Freédericksz transition (FT) effect stimulated by UV light intensity. A prototype of phase grating has also been devised based upon the observed FT-enhanced effect that has a prospect in certain photonic devices of dynamic and reversible light manipulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.