title: Effect of the Functional Groups of Racemic Rodlike Schiff Base Mesogens on the Stabilization of Blue Phase in Binary Mixture Systems.
abstract: Four series of rodlike racemic Schiff base mesogens possessing different alkyl chains and two types of linkages, ester and alkynyl linkages, were synthesized and applied to induce cubic blue phases (BPs) in simple binary mixture systems. The mesophases of these Schiff base mesogens were confirmed by variable-temperature X-ray diffraction and the characteristic texture from polarized optical microscopy (POM). In general, when chiral additive S-(+)-2-octyl 4-(4-hexyloxybenzoyloxy)benzoate (S811; 20-40 wt %) is added into the rodlike racemic salicylaldimine-based mesogens, the cubic BPs could be observed and its temperature range is larger than 20 K. The widest temperature range of the cubic BP (35 K) can be observed in the blending mixture composed of rodlike racemic salicylaldimine-based mesogen OH-TInpossessing alkynyl linkage and 35-40 wt % S811. However, Schiff base mesogens possessing alkynyl linkage show a direct isotropic to chiral nematic transition when equal amount of chiral dopant is added. Notably, the termination temperature of BPs is very close to room temperature (ca. 35 °C) after 40.0 wt % S811 is added into the salicylaldimine-based mesogens possessing terminal alkyl chains and ester linkage. Interestingly, wide BPs (>30 K) can also be induced by adding chiral additive 1,4:3,6-dianhydro-2,5-bis[4-(n-hexyl-1-oxy)benzoic acid]sorbitol (ISO(6OBA)2) with a high helical twisting power into the racemic Schiff base mesogen possessing ester linkage. Cubic BPI and BPII can be confirmed by reflectance spectra and POM. The results of reflectance spectra indicate that the binary mixture composed of salicylaldimine-based mesogens and S811 easily exhibits a supercooling effect and induces BPI. However, only BPII can be observed in all binary mixtures containing Schiff base mesogens. On the basis of our experimental results and molecular modeling, we suppose that the values of biaxiality, polarizability, and the dipole moment of molecular geometry are the main factors that affect BP stabilization.
authors.affiliation: Department of Chemical Engineering, Tatung University , Taipei 104, Taiwan.
authors.forename: Chiung-Cheng
authors.identifier: 0000-0001-7187-8900
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Department of Chemical Engineering, Tatung University , Taipei 104, Taiwan.
authors.forename: Zong-Ye
authors.initials: ZY
authors.lastname: Wu
authors.affiliation: Department of Chemical Engineering, Tatung University , Taipei 104, Taiwan.
authors.forename: Bing-Han
authors.initials: BH
authors.lastname: Sie
authors.affiliation: Department of Chemical Engineering, Tatung University , Taipei 104, Taiwan.
authors.forename: We-Hao
authors.initials: WH
authors.lastname: Chou
authors.affiliation: Department of Chemical Engineering, Tatung University , Taipei 104, Taiwan.
authors.forename: Yu-Chang
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Department of Chemical Engineering, Tatung University , Taipei 104, Taiwan.
authors.forename: Mei-Ching
authors.initials: MC
authors.lastname: Yu
authors.affiliation: Department of Molecular Science and Engineering, National Taipei University of Technology , Taipei 106, Taiwan.
authors.forename: Bo-Hao
authors.initials: BH
authors.lastname: Chen
authors.affiliation: Department of Molecular Science and Engineering, National Taipei University of Technology , Taipei 106, Taiwan.
authors.forename: I-Jui
authors.initials: IJ
authors.lastname: Hsu
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 300, Taiwan.
authors.forename: Lai-Chin
authors.initials: LC
authors.lastname: Wu
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 300, Taiwan.
authors.forename: Jey-Jau
authors.initials: JJ
authors.lastname: Lee