Mesomorphic and Anisotropic Properties of Trans-4-(4-Pentylcyclohexyl) Benzonitrile Doped with Chiral (Bis)Camphoralidene-Ethylenediamine

The mesomorphic, optical, orientation, and dielectric properties of a nematic liquid crystal (LC) of 4-pentyl-cyclohexyl-4-benzonitrile (5PCH) doped with optically active (bis)camphoralidene-ethylenediamine (C2-bisCamN) have been studied. On the basis of the analysis of mesophase textures, the chiral nematic induction has been detected with the addition of dopant. The helical pith of the induced chiral nematic in mixtures has been measured by the Grandjean–Cano method and the helical twisting power has been estimated. It has been shown that the chiral induction effectiveness decreases with increasing dopant concentration because of association. The clearance temperatures of the mixtures have been measured and the degree of destabilization of the mesophase with the introduction of dopant was assessed by the method of the polarization thermomicroscopy. The effect of a chiral dopant on the mesophase anisotropic characteristics such as: dielectric permeability and birefringence, has been studied. It has been found that the introduction of C2‑bisCamN and the formation of a chiral mesophase are accompanied by a decrease in dielectric and optical anisotropy and orientational ordering. In this case, the main contribution to the change in anisotropic characteristics has been made by the helical twisting and the local orientation of the “quasi-nematic” layers. The associative state of the mesophase of the binary systems based on the strongly polar cyan derived LCs has been evaluated using the Kirkwood correlation factor. A decrease in the degree of the antiparallel dipole-dipole association of 5PCH with an increase in the concentration of the additive has been shown. The optimized structures of the monomers and dimers of 5PCH, C2-bisCamN, and solvates based on them have been obtained using quantum chemical calculations. Analysis of the geometric parameters (anisotropy of shape and molar volumes), polarity, optical activity, and the stability energies of the monomers and supermolecules has allowed us to identify camphorodiimine associates as the most likely structures responsible for the properties of the induced chiral mesophase in the 5PCH + C2-bisCamN system.