Zavora L. Manifestations of molecular polymorphism and supramolecular ordering in mesomorphic systems with functionally active dopants

The work is devoted to peculiar features of supramolecular structure of functionally active organic substances manifested in mesomorphic and optical properties of liquid crystalline (LC) media doped with these substances. Effects of a number of organic luminophores (o-POPOP, stilbene, p-terphenyl, pyrene, etc.), anthraquinone dyes, and other substances used as functionally active dopants on helical twisting and isotropic transition temperatures in cholesteric matrices of different nature have been analyzed. It has been established that the degree of molecular anisotropy is a major factor determining the increase in helical twisting upon addition of non-chiral dopants into cholesteric mixtures. Significant deviations observed in some cases show evidence of specific intermolecular interactions between the components of the system. The method based on analysis of temperature and concentration dependences of the helical pitch and relative birefringence of cholesteric matrices with functionally-active dopants is used for the first time to study molecular polymorphism in several organic substances (aggregation of anthraquinone (AQ) dyes, formation of complexes of imidazole and matrix components, photoinduced transformations of aziridine derivatives, etc.). Effects of liquid crystalline ordering on luminescence spectra of several organic substances have been studied for the first time. It was established that luminescence band shifts for organic luminophores reflect changes in the molecular structure induced by the liquid crystalline medium. Majority of the studied functionally active substances showed good solubility in mesomorphic systems based on cholesterol esters and organic salts. This makes such systems promising for practical applications.