Mesomorphic Organization and Thermochromic Luminescence of Dicyanodistyrylbenzene-Based Phasmidic Molecular Disks: Uniaxially Aligned Hexagonal Columnar Liquid Crystals at Room Temperature with Enhanced Fluorescence Emission and Semiconductivity

Authors

  • Seong-Jun Yoon,

    1. Center for Supramolecular Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea
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  • Jong H. Kim,

    1. Center for Supramolecular Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea
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  • Kil Suk Kim,

    1. Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, CNRS-Université de Strasbourg, 67034 Strasbourg Cedex 2, France
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  • Jong Won Chung,

    1. Center for Supramolecular Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea
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  • Benoît Heinrich,

    1. Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749, Korea
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  • Fabrice Mathevet,

    1. Laboratoire de Chimie des Polymères-UMR 7610 Université Pierre et, Marie Curie, 75252 Paris Cedex 5, France
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  • Pyosang Kim,

    1. Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, CNRS-Université de Strasbourg, 67034 Strasbourg Cedex 2, France
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  • Bertrand Donnio,

    1. Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749, Korea
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  • André-Jean Attias,

    1. Laboratoire de Chimie des Polymères-UMR 7610 Université Pierre et, Marie Curie, 75252 Paris Cedex 5, France
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  • Dongho Kim,

    Corresponding author
    1. Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, CNRS-Université de Strasbourg, 67034 Strasbourg Cedex 2, France
    • Dongho Kim, Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.

      Soo Young Park, Center for Supramolecular Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea

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  • Soo Young Park

    Corresponding author
    1. Center for Supramolecular Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea
    • Dongho Kim, Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.

      Soo Young Park, Center for Supramolecular Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea

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Abstract

A new dicyanodistyrylbenzene-based phasmidic molecule, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(3,4,5-tris(dodecyloxy)phenyl)acrylonitrile), GDCS, is reported, which forms a hexagonal columnar liquid crystal (LC) phase at room temperature (RT). GDCS molecules self-assemble into supramolecular disks consisting of a pair of molecules in a side-by-side disposition assisted by secondary bonding interactions of the lateral polar cyano group, which, in turn, constitute the hexagonal columnar LC structure. GDCS shows very intense green/yellow fluorescence in liquid/solid crystalline states, respectively, in contrast to the total absence of fluorescence emission in the isotropic melt state according to the characteristic aggregation-induced enhanced emission (AIEE) behavior. The AIEE and two-color luminescence thermochromism of GDCS are attributed to the peculiar intra- and intermolecular interactions of dipolar cyanostilbene units. It was found that the intramolecular planarization and restricted molecular motion associated with a specific stacking situation in the liquid/solid crystalline phases are responsible for the AIEE phenomenon. The origin of the two-color luminescence was elucidated to be due to the interdisk stacking alteration in a given column driven by the specific local dipole coupling between molecular disks. These stacking changes, in turn, resulted in the different degree of excited-state dimeric coupling to give different emission colors. To understand the complicated photophysical properties of GDCS, temperature-dependent steady-state and time-resolved PL measurements have been comprehensively carried out. Uniaxially aligned and highly fluorescent LC and crystalline microwires of GDCS are fabricated by using the micromolding in capillaries (MIMIC) method. Significantly enhanced electrical conductivity (0.8 × 10−5 S•cm−1/3.9 × 10−5 S•cm−1) of the aligned LC/crystal microwires were obtained over that of multi-domain LC sample, because of the almost perfect shear alignment of the LC material achieved in the MIMIC mold.

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