In ionic liquid crystals (ILCs), the properties of ionic liquids and liquid crystals are combined.¹ The introduction of anisotropy in an electrolyte leads to an interesting set of properties, which has been used, for example, to form efficient one-dimensional ion conductors^2a and a medium to produce anisotropic conducting polymer films by means of electro-chemical polymerization.^2b

Traditional liquid crystals are built-up from an rigid rod-shaped aromatic core, substituted with two aliphatic tails. Ionic liquid, however, are frequently made up from a small ionic aromatic group, such as imidazolium or pyridinium groups, which are substituted by one or multiple aliphatic tails. In most reports on ILCs, one of the alkyl groups has been extended, resulting in the formation of mesophases or a common liquid crystalline pattern has been modified by attaching one or more imidazolium groups at the end of a tail/spacer. So far, only one example of an ILC which approaches the anisotropic shape of classical liquid crystal has been reported.³

We have prepared a series of ILCs that bridges the gap between traditional liquid crystals and traditional ionic liquids. In these systems, an imidazolium group is incorporated into the aromatic core, see Figure. This structure contains many structural parameters to manipulate the liquid crystal properties, including the substitution pattern, the counter ion as well as the size of the aromatic core. The chemistry towards this new class of liquid crystals and their mesomorphic behavior will be discussed.

In addition, we report on the application of selected mesogens as an anisotropic medium for electro-chemical polymerizations.

References: 1 K. Binnemans Chem. Rev. 2005, 105, 4148-4204. 2 (a) M. Yoshio, T. Kagata, K. Hoshino, T. Mukai, H. Ohno, T. Kato J. Am. Chem. Soc. 2006 ASAP article. (b) J. F. Hulvat and S. I. Stupp Angew. Chem. Int. Ed. 2003, 42, 778-781. 3 J.M. Suisse, S. Bellemin-Laponnaz, L. Douce, A. Maisse-Francois, R. Welter Tetrahedron Lett. 2005, 46, 4303-4305.