Lithium Salt Complexes of Laterally Fluorinated Dimeric Liquid Crystals Containing Oxyethylene Moieties : Phase Transition Behavior and Ionic Conductivity

Abstract

We developed new ion conductive liquid-crystalline materials using of oligo(ethylene oxide) moieties. We focused on negative dielectric anisotropy and smectic liquid crystallinity in relatively low temperature range of lateral fluorine(s)-substituted liquid crystals. In the present study, we synthesized fluorine-substituted mesogenic twin molecules containing an oxyethylene moiety. The complexation of the compound with lithium triflate induced an improved thermal stability of the smectic phase. The degree of the positive deviation by the complexation was up to 100℃. The stabilization was not observed for the complexes of a homologous compound without the fluorine substituent. 1^<19>F NMR spectra suggested that the significant stabilization was attributed to interaction between the fluorine and lithium cation. When the mesogenic core of the complex formed a homeotropically aligned monodomain, the ionic conductivity along the layer of the oxyethylene moiety became higher than that for the unaligned one. This result suggests that long range conductive paths have been formed in the complex.