title: Microwave-assisted synthesis, structure, and tunable liquid-crystal properties of 2,5-diaryl-1,3,4-thiadiazole derivatives through peripheral n-alkoxy chains.
abstract: A series of substituted 2,5-diaryl-1,3,4-thiadiazole derivatives are prepared by microwave-assisted synthesis in the absence of an organic solvent. All derivatives are well characterized by (1)H and (13)C NMR, MS, and elemental analyses. The X-ray crystal structure of 2,5-di-(4-decyloxyphenyl)-1,3,4-thiadiazole reveals the tilt lamellar arrangement of rod-shaped molecules, which are stabilized by a variety of weak non-covalent interactions. The liquid crystalline properties are studied by polarized-light optical microscopy (POM), differential scanning calorimetry (DSC), and in situ variable temperature X-ray diffraction (VTXRD). By variations in the peripheral n-alkoxy chains, the calamitic mesogens exhibit enantiotropic smectic (SmC and/or SmA) mesophases with wide mesomorphic temperature ranges, whilst the disc-like mesogens form hexagonal columnar mesophase (Col(h)) at room temperature. The bulk electrical conductivity values of the smectic mesophases of 1-3 are in the range of 10(-3)-10(-4) S cm(-1), which are slightly higher than that of their solid films. In contrast, the solid film made from 2,5-di-(3,4,5-trioctyloxyphenyl)-1,3,4-thiadiazole shows poor conductivity (2x10(-7) S cm(-1)).
authors.affiliation: Department of Chemistry, Nankai University, 94 Weijin Road, Tianjin, 300071, PR China. hanjie@nankai.edu.cn
authors.forename: Jie
authors.initials: J
authors.lastname: Han
authors.forename: Xiao-Yong
authors.initials: XY
authors.lastname: Chang
authors.forename: Li-Rong
authors.initials: LR
authors.lastname: Zhu
authors.forename: Mei-Li
authors.initials: ML
authors.lastname: Pang
authors.forename: Ji-Ben
authors.initials: JB
authors.lastname: Meng
authors.forename: Stephen Sin-Yin
authors.initials: SS
authors.lastname: Chui
authors.forename: Siu-Wai
authors.initials: SW
authors.lastname: Lai
authors.forename: V A L
authors.initials: VA
authors.lastname: Roy