Liquid Crystalline Mixtures Consisting of Mesogenic Gadolinium Complex and Nematic Liquid Crystals

Abstract
The introduction of a lanthanide ion into a liquid crystal molecule allows one to combine the orientational behavior of mesophases with high anisotropy of magnetic susceptibility and luminescent properties of lanthanide ions. This gives the opportunity to approach the creation of multifunctional materials with unusual electrical, magnetic, optical, and luminescent properties. Nematic phase is the least viscous of all types of mesophases, and this property determines the wide possibilities for its potential applications in optoelectronics. The existence of nematic phase in lanthanide complexes is a very promising, but rarely encountered property. In this regard, urgent and practically important task is obtaining lanthanide-containing liquid crystal systems exhibiting nematic mesomorphism in a wide temperature range. This work describes the preparation of a liquid crystalline adduct of tris(β-diketonate)gadolinium (III) with 5,5'-diheptadecyl-2,2'-bipyridine. The adduct exhibits smectic and nematic mesomorphism. The possibility of obtaining homogeneous nematic mixtures based on the synthesized Gd(CPDk_3-5)₃Bpy_17-17 complex and organic liquid crystals: 4-n-heptyloxy-4'-n-cyanobiphenyl, 4-(nonyloxy)benzoic acid, (E)-1-(4-butylphenyl)-2-(4-(heptyloxy)phenyl)diazene and 1-(4-fluorophenyl)-3-(4-(4-propylcyclohexyl) phenyl)propan-1,3-dione, is shown. Compositions with different ratios of components have been obtained. They possess a wide temperature range of nematic mesophase. Phase diagrams of the compositions were constructed with the use of polarization optical microscopy and differential scanning calorimetry.

Keywords: liquid crystals, lanthanide complexes, homogeneous mixture, nematic, smectic