The effect of various functional groups on mesophase behavior and optical property of blue phase liquid crystal compounds based on (-) menthol

In order to explore the effect of various functional groups on the mesomorphic properties, a series of menthol based blue phase liquid crystal compounds (A, B1, B2, C1, C2, D1, D2) with various core structures in the molecules were synthesized. Their chemical structures and phase behavior were characterized with FT-IR, H-1 NMR, differential scanning calorimeter (DSC) and polarizing optical microscopy (POM). The selective reflection and photoisomerization were investigated with ultraviolet/visible (UV/VIS) spectrometer. In our case, all BPLCs showed oily streak texture with selectively reflection and blue phase (BP), irrespective of the structure of mesogenic cores. This demonstrated that (-) menthol had high chirality, and via succinyloxy spacer group could drive molecules to arrangement in double twist cylinders of BP. The length-to-diameter ratio, the bridge bond in the aryl rings and the conjugate action in the mesogenic core had a significant effect on T-m, T-i and temperature range of BP. BPLC A without conjugated structure in three-benzene mesogenic core revealed a larger temperature range of BP than other BPLCs with conjugated structure. (C) 2018 Elsevier B.V. All rights reserved.