T-Shaped Ionic Liquid Crystals Based on the Imidazolium Motif: Exploring Substitution of the C-2 Imidazolium Carbon Atom

Research output: Contribution to journalArticlepeer-review

Authors

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

Institutes & Expert groups

  • KUL - Katholieke Universiteit Leuven

Documents & links

DOI

Abstract

In this contribution the first examples of so-called rigid-core, Tshaped 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 Pm3m structure. To the best of our knowledge, this is the first example of a thermotropic cubic mesophase of this symmetry.

Details

Original languageEnglish
Pages (from-to)4291-4306
JournalChemistry - A European Journal
Volume17
Issue number5
DOIs
Publication statusPublished - Apr 2011

Keywords

  • cubic phases, imidazolium cations, ionic liquids, liquid crystals, self-assembly

ID: 236635