The object of investigation: synthesis of new mesogenic-like phosphonic acids and dependence of stability of nanoparticles colloids in liquid crystals on molecular structure of the ligands on the nanoparticles surface. The purpose of research - the creation of new mesogenic-like ligands of different molecular structure and establishment of influence of structure of the ligands on their ability to stabilize the nanoparticles colloid in thermotropic liquid crystals with great practical value - with the nematic and smectic C phases. Methods: methods of organic synthesis, high performance liquid chromatography (HPLC), matrix-assisted laser desorption/ionization (MALDI spectroscopy), gas chromatography (GC), UV, IR, NMR, mass and fluorescence spectroscopy, polarization (POM) and fluorescence (FM) optical microscopy, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), fluorescence correlation spectroscopy (FCS), energy dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), X-ray fluorescence analysis (XRF), X-ray powder diffraction (XRD). Theoretical and practical results: a series of ligands with linear mesogenic-like alkylftoroterfenyl, alkylbifenyl-4-yl-benzoate and cyanobiphenyl promesogenic substituents and terminal anchoring (phosphonate) group were synthesized. A methods for the synthesis of T-shaped 4,4'-dialkylterphenyls comprising lateral w-phosphonoalkyl function and dendritic derivatives of gallic acid comprising three promesogenic fragments and terminal w-phosphonoalkyl group were elaborated, alternative synthetic approaches were compared and their mesomorphic properties were investigated. The regularities of influence of ligands structure on their stabilizing ability in liquid crystal nanocomposites were found and it was shown that the most effective are mesogenic-like dendritic ligands combined with aliphatic ones which allows to obtain thermodynamically stable nanoparticles colloids in liquid crystals. A pronounced magneto-optical effect was found in dispersions of rod-shaped ferromagnetic gamma-Fe2O3 nanoparticles modified with cyanobiphenyl-derivative linear ligand in a nematic liquid crystal. Novelty: a general structure and preparative methods for synthesis of three types of new ligands: linear, dendritic and T-shaped phosphonic acids containing promesogenic groups were elaborated. True colloids of nanoparticles in liquid crystals were first obtained and proved with the use of dendritic promesogenic phosphonic acids. The key intermediate based on gallic acid with w-phosphonoalkyl group, which obtained in synthetic scheme of dendritic phosphonic acids, provides a convenient way for efficient synthesis of stabilizers of nanoparticles dispersions in various LCs or other organic media. An excessive alkylation of esters of gallic acid with promesogenic bromides requires an additional moisture removal, which is achieved with the use of activated zeolites. In the synthesis of arylboronic acids from aryl bromides replacement aryllithium intermediates to the corresponding aryl magnesiumbromides and borilation at temperature of -10 - +5 °C, instead of -70 °C, can significantly simplify and reduce the cost the procedure for obtaining the desired products without yield reducing. The most effective for stabilizing the nanoparticle dispersions in nematic liquid crystals is a sparse and highly flexible architecture of nanoparticles shell capable of efficient interacting with molecules of liquid crystal. Such a shell can be constructed with a combination of dendritic mesogenic-like ligands comprising terminal alkyl groups and short chain alkylphosphonic acids in a ratio of 1:4. Degree of implementation: the application of developed mesogenic-like ligands allows to obtain thermodynamically stable dispersions of quantum dots in LC; stable LC dispersion of magnetic nanoparticles in a concentration sufficient to reduce the threshold value of the magnetic field of the Freedericksz transition in half compared with the pure 4-pentyl-4'-cyanobiphenyl; a uniform distribution of semiconductor nanoparticles within the conductive polymer matrix based on polyvinylcarbazole.These are prerequisite for the further advancement of basic research and development of practical applications of these new composite materials. Sphere of application: scientific research, the development of novel photovoltaic and light-emitting devices, sensors of weak magnetic fields, liquid crystals with improved performance.
