Phase retardation of both extraordinary and ordinary polarized rays passing through a liquid crystal (LC) cell with homogeneous and inhomogeneous LC director distribution is calculated as a function of the LC pretilt angle ${\text{θ}}_{\text{0}}$ on the cell substrates in the range $0\le {\text{θ}}_{\text{0}}\le 90°$. The LC pretilt on both substrates can have the same or opposite direction, thereby forming homogeneous, splay, or bend director configurations. At the same pretilt angle value, the largest phase retardation $\Delta \Phi$ is observed in splay LC cells, whereas the smallest phase retardation is observed in bend cells. For the ${\text{θ}}_{\text{0}}$ values close to 0, 45°, and 90°, analytical approximations are derived, showing that phase retardation depends on LC birefringence variation.

A cholesteric liquid crystal (CLC) – cholesteryl tridecylate (X-20) was doped with nanoparticles of shungite carbon (Sh) to effectively improve some physicochemical properties of the CLC matrix for the further use in electronic devices. The influence of Sh (concentration of 0.005 and 0.02 wt. %) on phase transition temperatures of X-20 was studied. Addition of 0.005 wt. % of Sh shifts phase transition temperatures upward, while the concentration increase to 0.02 wt. % leads to the opposite effect. These data were taken into account during the study of dielectric properties in different phase states. The dielectric properties were studied in the frequency range from 20 Hz to 10 MHz. Only for the system X-20/Sh (0.02 wt. %), dispersion of the dielectric permittivity was observed. The dispersion was caused by the appearance of additional relaxation processes and it was substantially more extended than the classical Debye theory suggests. The results of the research show that the ‘CLC – Sh nanoparticles’ composites can be used as promising materials to increase the efficiency of radio electronics devices.

The effect of gold nanoparticles on the dielectric, electro-optical, and rheological properties of the ZhK-1289 liquid-crystal mixture that define the response time of liquid-crystal devices with a concentration range of 0.06–5 wt% was investigated in this study. A phase diagram of the obtained composites was formed demonstrating an increase in the clearing temperature and a broadening of the mesophase existence range in the case of doping nanoparticles. It was found that in the obtained dispersions there are structural rearrangements in the low concentration range leading to an increase in the lateral bending stiffness of the liquid-crystal matrix, a decrease in the response time and threshold voltage of the Freedericksz transition, and also an increase in the anisotropy of the dielectric permittivity and the refraction index. The improvement of the electro-optical performance of the liquid crystal can be caused by the nanoparticle adsorption of impurity ions, which reduces the field-screening effect in the liquid crystal. According to the results obtained in this study, the optimal values of the physical parameters of liquid-crystal composites doped with gold nanoparticles for their application in practice are achieved in a concentration range of 0.5–1 wt%.

The phase retardation difference, $\mathrm{\Delta }\mathrm{\Phi }$, is calculated for hybrid liquid crystal (LC) cells as a function of LC pretilt angles, ${\theta }_0^{(1)}$, ${\theta }_0^{(2)}$, on the opposite substrates of the cell for the case of an arbitrary angle of light incidence in the range from 0 to 90°. An LC director configuration is suggested for its application in optical compensators. Design and fabrication methods of hybrid aligned nematic (HAN) cells with an arbitrary LC pretilt angle are described. The LC pretilt angle is measured in the HAN cells with a given planar or vertical LC alignment on one of the substrates.

Microbial antibiotic resistance is an important global world health problem. Recently, an interest in nanoparticles (NPs) of silver oxides as compounds with antibacterial potential has significantly increased. From a practical point of view, composites of silver oxide NPs and biocompatible material are of interest. A borosiloxane (BS) can be used as one such material. A composite material combining BS and silver oxide NPs has been synthesized. Composites containing BS have adjustable viscoelastic properties. The silver oxide NPs synthesized by laser ablation have a size of ~65 nm (half-width 60 nm) and an elemental composition of Ag₂O. The synthesized material exhibits strong bacteriostatic properties against E. coli at a concentration of nanoparticles of silver oxide more than 0.01%. The bacteriostatic effect depends on the silver oxide NPs concentration in the matrix. The BS/silver oxide NPs have no cytotoxic effect on a eukaryotic cell culture when the concentration of nanoparticles of silver oxide is less than 0.1%. The use of the resulting composite based on BS and silver oxide NPs as a reusable dry disinfectant is due to its low toxicity and bacteriostatic activity and its characteristics are not inferior to the medical alloy nitinol.