Photoswitchable Bent-Core Nematic Liquid Crystals with Methylated Azobenzene Wing Exhibiting Optic-Field-Enhanced Fréedericksz Transition Effect

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 (-CH3) substituent in respect of the azo (-N=N-) linkage in the molecule. Single crystal X-ray diffraction (SCXRD) 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 photo-masking 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 compound (2/12) was studied to observe the optically-enhanced Freedericksz 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 ha...