In and out – new ionic mesogens based on a cyanoborate building block and lipophilic or hydrophilic counter ions

Abstract. New ionic mesogens have been prepared based on a cyanoborate head group, which is tethered to a lipophilic periphery via a short flexible spacer. As counter ions, either tetra-n-butyl ammonium cations or sodium and potassium cations stabilized by 18-crown-6 have been used. Although all compounds realise SmA enantiotropic mesomorphism, X-ray diffraction, modelling and solid-state NMR uncover distinct self-assembly of the LC materials in double layers. While the ammonium ions are located in-between the borate anions and are in contact with spacers and aromatic units, the crown ethers with the coordinated alkali metal cations are completely nanosegregated between two borate anion layers. Homogenous and homeotropic alignment has been achieved. Electrical impedance studies confirm two to three orders of magnitude higher conductivity of the correctly-aligned samples in the single-ion conductor. Values of ca. 10-4 Scm-1 in the SmA phase at 85 °C and 10-5 Scm-1 at 40 °C have been obtained.