Chiral transfer from (1S, 2R, 5S)-(+)-menthol and its acetate to polar liquid crystal: Role of H-bond and dipole-dipole interaction

Abstract

The mesomorphic and anisotropic properties of the induced chiral nematic phase in a mixture of substituted cyanobiphenyls (CB6) doped with chiral (1S, 2R, 5S) - (+) – menthol and its acetate are studied. The clearing temperatures and the pitch were measured, and the value of the helical twisting power β were calculated. An insignificant effect of chiral menthol, its racemate and acetate on the clearing temperature of the LC mixture, birefringence, and orientational ordering is shown. At the same time, the dielectric anisotropy of the helical phase CB6 + chiral dopant was found to strongly depend on the degree of mesophase twisting and the intensity of the magnetic field applied to the sample. Similar effects were shown in the study of kinematic viscosity. Based on the results of the Kirkwood's correlation parameter analysis and quantum-chemical calculations, it was shown that the introduction of the chiral mentol and menthyl acetate dopant leads to a change in the associative state of the LC matrix due to the formation of hydrogen bond of menthol and dipole-dipole contact of menthyl acetate with host molecules.