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M. E. Karyakin¹, A. S. Krupin¹, A. A. Knyazev¹, Yu. G. Galyametdinov^1,2

Author affiliations
¹Kazan National Research Technological University,
68 Karl Marx St., Kazan, 420015, Russia
²Kazan E. K. Zavoisky Physical Technical Institute,
10/7 Sibirsky Tract, Kazan, 420029, Russia
E-mail: karyakin-maksim @list.ru

Abstract
Liquid crystal mixtures based on the tris [1-(4-trans-(4-propylcyclohexyl)phenyl)-octane-1,3-diono]-[5,5'-diheptadecyl-2,2'-bipyridine]europium complex (Eu(CPDk_3-5)₃Bpy_17-17) and the conducting poly(9,9-di-n-octylfluorenyl-2,7-diyl) polymer (PFO) were obtained. It was found that the resulting mixtures with a continuous solid solution belong to isomorphic systems of the Rozeboom type I and exhibit nematic mesomorphism at any ratio of components. Upon cooling to room temperature, the LC mixtures were vitrified with the preservation of the mesophase packing. Using the orienting substrates, a planar-oriented film material based on an LC mixture containing 10 mol. % of PFO and 90 mol. % of the Eu(CPDk_3-5)₃Bpy_17-17 complex was created. The dichroic ratio of photoluminescence R (it is the ratio of the luminescence intensities at 0° and 90°) of the obtained material is 5.4 at a wavelength of 438 nm and 3.2 at a wavelength of 613 nm. It was found that the obtained film materials are capable of changing the luminescence color from light red to dark blue, depending on the UV irradiation wavelength or upon changing the angle between the polarizer plane and the molecular orientation direction. Thus, the possibility of obtaining oriented films of lanthanide-containing liquid-crystal mixtures with controlled polarization and luminescence color has been shown.

Keywords: liquid crystal mixture, nematic, europium(III) complex, polymer, polarized luminescence