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    Please use this identifier to cite or link to this item: https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/79692

    Title: Enantiotropic nematics from cross-like 1,2,4,5-tetrakis(4'-alkyl-4-ethynylbiphenyl)benzenes and their biaxiality studies
    Authors: Chen, Hsiu-Hui;Lin, Hsing-An;Lai, Yin-Hui;Lin, Shu-Yu;Chiang, Chien-Hung;Hsu, Hsiu-Fu;Shih, Tzenge-Lien;Lee, Jey-Jau;Lai, Chien-Chen;Kuo, Ting-Shen
    Contributors: 淡江大學化學學系
    Keywords: arenes;mesogens;nematic phase;liquid crystals;X-ray diffraction
    Date: 2012-07
    Issue Date: 2013-01-09 07:40:02 (UTC+8)
    Publisher: Weinheim: Wiley - V C H Verlag GmbH & Co. KGaA
    Abstract: The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross-shaped compound 3, which showed enantiomeric nematic phase behavior. This cross-like core structure could alternatively be viewed as two fused V-shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface-induced biaxiality was evidenced by optical studies. Cluster-size analysis within the nematic phase of compound 3 revealed the formation of meta-cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small-angle 2D X-ray diffraction patterns of magnetic-field-aligned samples indicated that the nematic phase was composed of small smectic C-like clusters with the tilting of molecules within the clusters. The wide-temperature-range enantiomeric nematic phase of cross-like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent-rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher-order liquid-crystalline phases and crystallization, for future biaxial investigations.
    Relation: Chemistry - A European Journal 18(31), pp.9543–9551
    DOI: 10.1002/chem.201103453
    Appears in Collections:[Graduate Institute & Department of Chemistry] Journal Article

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