Ion-conductive liquid crystals: Formation of stable smectic semi-bilayers by the introduction of perfluoroalkyl moieties

Liquid-crystalline compounds 1 and 3 having perfluoroalkyl-terminated mesogens at both ends of poly(ethylene oxide) chains have been prepared. These compounds show smectic A (S_A) and C phases over 100°C. The S_A-Iso (isotropic) transition temperatures are higher by about 70°C than those of the corresponding alkyl-substituted compounds 2 and 4. The incorporation of lithium triflate into 1 and 3 widens the temperature ranges of the S_A phases for the resulting complexes. The complexes of 1 and 3 containing 50 mol-% of lithium triflate exhibit columnar phases. The ionic conductivities of the homotropically aligned complexes based on 1 along the direction perpendicular to the molecular director of the S_A phases are higher than those of the corresponding compound of 2. The increase of the ionic conductivities as well as the stabilization of the smectic phases for these perfluoroalkyl-terminated compounds may be due to the formation of more stabilized layered structures through the intermolecular interactions among the perfluoroalkyl moieties.