T-shaped ionic liquid crystals based on the imidazolium motif: Exploring substitution of the C-2 imidazolium carbon atom

Karel Goossens, Sil Wellens, Kristof Vana Hecke, Luc Van Meervelt, Thomas Cardinaels, Koen Binnemans

    Research outputpeer-review


    In this contribution the first examples of so-called rigid-core, T-shaped imidazolium ionic liquid crystals, in which the C-2 atom of the imidazolium ring is substituted with an aryl moiety decorated with one or two alkoxy chains, are described. The length of the alkoxy chain(s) was varied from six to eighteen carbon atoms (n=6, 10, 14-18). Whereas the compounds with one long alkoxy chain display only smectic A phases, the salts containing two alkoxy chains exhibit smectic A, multicontinuous cubic, as well as hexagonal columnar phases, as evidenced by polarising optical microscopy, differential scanning calorimetry, and powder X-ray diffraction. Structural models are proposed for the self-assembly of the molecules within the mesophases. The imidazolium head groups and the iodide counterions were found to adopt a peculiar orientation in the central part of the columns of the hexagonal columnar phases. The enantiotropic cubic phase shown by the 1,3-dimethyl-2-[3,4-bis(pentadecyloxy) phenyl]imidazolium iodide salt has a multicontinuous Pm$\bar 3$m structure. To the best of our knowledge, this is the first example of a thermotropic cubic mesophase of this symmetry.

    Original languageEnglish
    Pages (from-to)4291-4306
    Number of pages16
    JournalChemistry - A European Journal
    Issue number15
    StatePublished - 4 Apr 2011

    ASJC Scopus subject areas

    • Catalysis
    • General Chemistry
    • Organic Chemistry

    Cite this