Bukalo V. Optical Spectroscopy of the Structural Transformations in Mesogenics with Benzylidene-Aniline Core.

Phase diagrams of aminoxybenzylidene-toluidine (ABT) under quick and slow (1K/min) cooling of the sample and corresponding relationship of spectra with structure are established from analysis of Raman spectra. It was found that structure of stable crystalline state obtained by heating of supercooled sample coincides with structure of crystalline phase in which nematics transforms at slow cooling. It was established by experiment and theoretically predicted that vibrational band widths and forms for liquid crystalline, isotropic liquid and amorphous solid states of ABT coincide. The relaxation properties of structural transformation amorphous phase ѕ metastable crystal were studied and activation energy of it was estimated from analysis of spectra changes. It is investigated the manifestation of the structural relaxation processes in liquid crystalline glass in vibrational Raman spectra. It is determined the temperature dependence of structural relaxation time of amorphous aminoxybenzylidene-toluidine in temperature region of glass phase crystallization and corresponding activation energy (21kJ/mol). From analysis of developments of structural transformations and conformational changes of ABT in Raman spectra it was found that topologic structure ordering at heating of glassed benzylidene-aniline objects is accompanied by unfreezing of molecular conformational mobility. The conformational peculiarities of various structural transformations in mesogenics with benzylidene-aniline core were investigated. The results of semi-empirical calculations of geometric parameters of stable conformers of investigated molecule of ABT and its vibrational spectra are cited. Via comparison of the modeling spectra with experimental Raman spectra and via analysis of electronic spectra of investigated sample it was established the conformational structure of obtained structural modifications of ABT: planar molecular geometry in stable crystalline state and perpendicular torsion angle between benzene rings of ABT molecule in m etastable crystalline phase. Liquid crystalline, amorphous solid and isotropic liquid states are mixtures of all possible conformers.