The Effect Of The Position Of Chiral (-)-Menthyl On The Formation Of Blue Phase And Mesophase Behavior In Biphenyl-Benzoate Liquid Crystals

Eight new chiral liquid crystal compounds 4-(4-menthyloxy-n-oxoalkanoyloxy) biphenyl-4'-yl 4-butoxybenzoates MnB4OB (n = 1-8), were prepared by modifying the position of chiral (-)-menthyl in the menthol based liquid crystal compounds through gradually increasing the alkyl chain length of the dicarboxylic spacer. All compounds were characterized by FT-IR and NMR spectroscopy in order to prove their chemical structures. Differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction were carried out to systematically investigate their phase transition behaviors. The position of chiral (-)-menthyl in relation to the core has a great effect on the formation of BPs and mesomorphic behaviors. Only CLCs M1B4OB and M2B4OB with short spacer chains presented blue phases. Furthermore, the length and parity of the flexible spacers have a profound influence on phase structures and phase transition behaviors. An odd-even effect is observed for these chiral liquid crystal compounds. (C) 2019 Elsevier B.V. All rights reserved.