On a Specific Intermolecular Interactions in Nematic Liquid Crystal Systems

Abstract

The aim of this study was the investigation of the molecular structure of Nematic Liquid Crystal Systems that are based on polar liquid crystals, whose molecules have a large dipole moment directed along the long axis of the molecule. The investigation has a practical importance in the development of the new LC materials for electro-optical systems. In this work, the investigation of a specific intermolecular interaction – the formation of charge transfer complexing (CTC) in LC systems − was carried out by UV and IR spectroscopy. A long−wavelength shift of the CTC absorption band is found. The complicated dependence of optical density of the absorption band of the donor and CTC on the initial donor concentration has been obtained. The correlation between the optical density of the absorption bands of the CTC and donor, on the one hand, and the phase diagram, on the other, was demonstrated to occur in the investigated systems. The analytical expressions for equilibrium constants of complexation process were derived, and the concentrations of the complexes were determined based on the absolute rates reaction theory.

Dynamical behaviour of phase transitions in liquid crystals under ultrasound field

“…On the other hand, the features of the NLC→IL phase transitions under an ultrasonic field have some common characteristics with similar transitions in binary systems of strongly and weakly polar NLC [16]. In this regard, the most significant fact is that due to the specific interactions in such systems, which lead to a decrease in interaction energy inside the LC clusters and facilitate the destruction of the short-range order, the processes of orientation "melting" and the destruction of the short-range order during the NLC→IL phase transition occur almost simultaneously, and as a result, during the NLC→IL phase transition, only one phase boundary is observed.…”

Molecular mechanism of smectisation and regulation of polymorphism in nematic liquid crystal systems

“…The correlation between the optical density of the absorption bands of the CTC and donor, on the one hand, and the phase diagram, on the other, was demonstrated to occur in the investigated systems [5]. The analytical expressions for equilibrium constants of complexation process were derived [5], and the concentration of the complexes were determined based on the absolute rates reaction theory [9]. These investigations have a practical importance in the development of the new LC materials for electro-optical systems and were carried out to establish the interrelation between the liquid crystalline state and the properties of molecules, their structural ordering and intermolecular interactions to predict and optimize the technological parameters of LCs in the areas of their practical application.…”

“…Formation of the CTC of simple 𝐷 𝐴 (𝐷-donor, 𝐴-acceptor) and complex 𝐷 2 𝐴 compositions was found [5]. The complicated dependence of the optical density of the absorption band of the donor and CTC on the initial donor concentration has been obtained.…”

“…The creation of such charge transfer complexes is a powerful and flexible instrument for modifying the structures and properties compared to those of the initial components [1][2][3]. In [4][5][6][7][8] the study of the molecular structure of nematic liquid crystal (NLC) systems that are based on polar liquid crystals, whose molecules have a large dipole moment directed along the long axis of the molecule (such as 4-n-buthyl-4 ′ -n ′ -heptanoiloxyazoxybenzene; n-cyanophenyl ester of n ′ -heptylbenzoic acid) as well as the investigation of a specific intermolecular interaction -the formation of charge transfer complexing (CTC) in LC systems were carried out by EPR, UV and IR spectroscopy.…”

“…The complicated dependence of the optical density of the absorption band of the donor and CTC on the initial donor concentration has been obtained. The correlation between the optical density of the absorption bands of the CTC and donor, on the one hand, and the phase diagram, on the other, was demonstrated to occur in the investigated systems [5]. The analytical expressions for equilibrium constants of complexation process were derived [5], and the concentration of the complexes were determined based on the absolute rates reaction theory [9].…”