The influence of the anchoring energy of a cholesteric liquid crystal (LC) with boundary surfaces on the critical thickness d & scy;of LC layer at which the cholesteric helix unwinds. For this purpose, within the framework of the continuum theory, expression for the free energy of the LC layer is obtained. It is shown that has the form of an expansion of the Landau free energy in powers of the order parameter, which is the angle of deviation of the director from the easy orientation axis. As a result, the dependence of d & scy;on the natural pitch of the cholesteric helix p0 was determined. It is shown that in the region of small values of p0 this dependence is quadratic, while in the region of large p0 it approaches linearity.
According to the significant progress in the synthesis and study of lanthanide-containing metallomesogens, a number of fundamental questions regarding the correlations between the structure, chemical composition, and functional properties of these compounds remain unresolved. The complexity of studying these objects is due to the lack of clear understanding of the mechanisms underlying their liquid-crystalline properties and photoluminescence effects. Moreover, there are limited possibilities for extensive experimental study of the influence of the central Ln(III) ion and ligands on the molecular structure and physicochemical behavior of the experimentally obtained compounds. In this article, the geometric and luminescence characteristics of mesogenic Ln(III) complexes with substituted beta-diketones and Lewis bases were examined with the help of the quantum-chemical methods and Judd-Ofelt theory. These complexes have not been studied previously using these approaches. The relationships between the positions of the molecules' lowest triplet and singlet excited states, luminescence intensity, the efficiency and directions of intramolecular energy transfer, as well as values of theoretical emission quantum yields have been explored. The simulation results demonstrate good agreement with available experimental data. The obtained information will allow to optimize the choice of the central Ln(III) ion due to ligand's environment in order to enhance the complexes' luminescence efficiency.
New potential physiologically compatible biotransport systems were obtained and characterized: microemulsions and lyotropic liquid crystals of the composition bis(2-ethylhexyl)sodium sulfosuccinate (AOT)/water/isopropyl myristate. It was shown that with an increase in the AOT content, changes in self-organization and a transition to more ordered liquid crystal structures occur. It was found that with the introduction of luminescent markers, the developed nanocarriers can be effective carriers in targeted drug delivery with a visualization effect in target cells. Solubilization of a small heme-containing protein cytochrome C in the obtained systems was studied. By modeling the conditions at the water / oil interface, the adsorption interaction of cytochrome & Scy; with the surfactant AOT was established. It was shown that the interaction of AOT and cytochrome C is affected by the presence of amino acids contained in the protein. The kinetics of mass transfer of cytochrome C through a semipermeable model membrane into physiological Ringer's solution was studied using the developed microemulsions and liquid crystalline mesophases. The concentration of the target component in the receiving medium was estimated by UV-spectroscopy. It was shown for the first time that in the case of microemulsions, the release has a two-stage nature, while for mesophases a slow prolonged release is characteristic. The obtained results can be useful in creating effective transport systems for the delivery of biologically active substances.
The formation of liquid crystalline (LC) phases in aqueous suspensions of cellulose nanocrystals (CNCs) largely depends on the geometric dimensions of the CNC particles, their concentration, polydispersity, and surface charge. Obtaining reproducible LC structures requires meticulous control over the particle production conditions that determine these properties. The objective of this work is to investigate the possibility of formation of LC phases in dilute aqueous suspensions of CNCs and the preservation of nematic and chiral nematic order in dried films. CNCs were prepared via sulfuric acid hydrolysis of filter paper. Their properties were characterized using transmission electron microscopy, polarized optical microscopy, FTIR spectroscopy, dynamic light scattering, X-ray diffraction and elemental analysis. The rheological properties of dilute CNC suspensions and the morphology of films formed from these suspensions were examined. Additionally, the effect of ultrasonic treatment on the properties of CNC suspensions was evaluated. It was found that LC phase formation begins at a CNC suspension concentration of approximately 1 wt
The phenomenon of reversible photoinduced optical anisotropy in colored organic glasses (TOSP brand mark) has been investigated. The glasses were manufactured on the basis of polymethylmethacrylate with azo dyes plasticized by dibutyl phthalate, their thickness was 5+ mm. Such materials are used for liquid crystal photoalignment. The objective of the investigation was to identify the possibility of forming photoinduced optical anisotropy in media, which thickness significantly exceeds the wavelength of visible radiation. Experimental studies were conducted by measuring the kinetics of birefringence under exposure to polarized radiation generated by a high-pressure mercury lamp and nitrogen laser LGI-21. It was found that the thick layers studied exhibit the effect of photoinduced anisotropy that is characterized by cyclic induction and erasure of birefringence when the polarization plane orientation of the activating radiation is periodically changed. The kinetics of photoinduced birefringence varies for samples with different azo dyes, which is related to the specific features of their photochemical stability and photochromic properties. For glasses based on photochemically stable azo dyes, the possibility of accumulating optical anisotropy with irradiation cycles was discovered, opening prospects for the development of bulk optical elements with three-dimensional distribution of polarization properties. The results obtained are of significant importance for the development of new optical and optoelectronic devices, including polarized optical elements, information display systems, and optical anti-counterfeiting protection.
