Vol 88, No 5 (2026)

The electrostatic interaction of two identical charged dielectric spheroidal particles in a symmetrical electrolyte solution is considered. Based on the Poisson–Boltzmann equation, the finite element method is used to calculate the forces with which particles repel each other, provided that the charge distribution on their surfaces does not change with the distance between them, and there is no external electrostatic field. The surface charge distribution on each particle is assumed to coincide with that of an isolated single particle at a prescribed surface potential value. It is found that, depending on the Debye length and the surface-to-surface separation between the particles, varying the longitudinal size of the particles – from oblate to prolate spheroids – can either increase or decrease the interaction force.

The kinetics of generation of the circular dichroism signals characteristic of the cholesteric liquid- crystalline dispersions of DNA were compared with the results of their detailed study using confocal microscopy. Three processes of the dispersed particle evolution have been experimentally confirmed (characteristic time intervals are given in brackets): 1) growth due to the attachment of DNA molecules (tens of seconds), 2) coalescence accompanied by rearrangement of the cholesteric layers (minutes) and, finally, 3) aggregation, resulting in the formation of large clusters of irregular shape, that has a threshold dependence on the concentration of the nucleic acid (hours). It has been suggested that the latter have no "integral" optical activity.

The interpolymer interaction in the lignosulfonate (LS)–chitosan (Chit) system, where chitosan was dissolved in aspartic acid (Chit·Asp), was studied, and the colloid-chemical regularities of macrophase separation accompanied by the formation of a water-insoluble polyelectrolyte complex (PEC) were established. Based on the concentration dependences of molar conductivity and pH, LS and Chit·Asp solutions were shown to exhibit polyelectrolyte properties. Using potentiometrically controlled stepwise mixing of polyelectrolyte solutions in two different sequences, the cloud points were determined and an empirical phase-state diagram of the LS–Chit·Asp systems was constructed. It was shown that, when the LS solution was added to the Chit·Asp solution, the onset of turbidity was observed at a conditional analytical ratio n(SO₃^–)/n(NH₃⁺) = 0.015–0.567, i.e., in the region of an analytical excess of Chit amino groups. In the reverse mixing sequence, when the Chit·Asp solution was added to the LS solution, initial turbidity was recorded at n(SO₃^–)/n(NH₃⁺) = 6.30–7.03, which corresponds to an analytical excess of LS sulfonate groups. Therefore, the transition of the system to macrophase separation is not limited to the achievement of conditional charge equivalence of the functional groups and substantially depends on the sequence of component addition, the local composition of the medium, and concentration and kinetic factors. A water-insoluble PEC was isolated from the LS–Chit·Asp systems and characterized using FTIR spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The combined data indicate the formation of an LS–Chit interpolymer complex involving electrostatic interactions between SO₃^– groups of LS and NH₃⁺ groups of protonated Chit, as well as hydrogen bonding. It was established that the phase behavior of the system is governed not only by the charge ratio of the components, but also by the mixing sequence and the conformational and associative features of natural polyelectrolytes in aqueous medium.

This article examines the possibility of controlling biocatalytic reactions in self-organizing systems using cytochrome C as a catalyst. It is known that it can speed up biological processes, acting as a catalyst for cellular respiration. Microemulsions based on sodium bis(2-ethylhexyl)sulfosuccinate (AOT) are of considerable interest as nanoscale transport and reaction systems in biocatalysis, as they are capable of stabilizing enzymes while maintaining their functional activity. In this study, three-component water/AOT/ isopropyl myristate systems of varying composition and degree of hydration were obtained. Structural and phase transformations in the studied systems were studied with an increase in the surfactant concentration from microemulsions to a liquid crystalline mesophase. It was found that the incorporation of cytochrome C into microemulsions results in its good solubilization, which leads to a slight decrease in their size and a narrower distribution of droplets in the system. The results of UV-Vis spectroscopy and luminescence showed the presence of adsorption interaction between the protein and the polar groups of AOT. The applicability of the resulting systems to biocatalysis was investigated using the example of guaiacol oxidation with hydrogen peroxide in the presence of cytochrome C. To controllably increase the yield of the catalytic reaction product, hydrophilic \(\mathrm{Cd}_{0.9}\mathrm{Mn}_{0.1}\mathrm{S} / \mathrm{ZnS}\) quantum dots stabilized with mercaptopropionic acid were added to the microemulsion. It was found that the yield of tetraguaiacol obtained in the reaction increases directly proportionally to the concentration of the introduced quantum dots. Thus, by using microemulsions as reaction media, we can accelerate or slow down catalytic processes.

Direct numerical simulations of the electrophoresis of a charged dielectric microparticle are performed within the framework of a coupled nonlinear Nernst-Planck-Poisson-Stokes system over a range from weak to strong electric fields. The aim of the study is to compare the electrophoretic mobility and the structure of ionic transport in polar and non-polar electrolytes at a fixed particle surface charge. To represent these two types of media, two characteristic values of the Debye length are considered, corresponding to a thin and a relatively thick electric double layer. The particle surface charge is fixed at a value for which pronounced nonequilibrium effects and deformation of the ionic cloud are expected at sufficiently high electric field strengths. Particular attention is paid to the dependence of the dimensionless mobility on the electric field strength and on the control parameter \(\kappa\) , which determines the intensity of electrokinetic coupling and the influence of hydrodynamics on ionic transport. It is shown that, as the field strength increases, the response becomes strongly nonlinear and is accompanied by enhanced concentration polarization and restructuring of the spatial distributions of ion concentrations and space charge. Parametric dependences of the electrophoretic mobility are compared for the two characteristic Debye lengths, and parameter regions are identified in which the difference between polar and non-polar media is primarily quantitative, as well as regions corresponding to a qualitative restructuring of the transport regime. For representative regimes, spatial distributions of the total ion concentration and charge density are presented, allowing the changes in mobility to be related to changes in the structure of ionic fluxes and the bulk electric force. The obtained results provide criteria for the onset of the nonequilibrium regime and may be used for interpreting experiments and designing electrokinetic microsystems in polar and non-polar electrolytes.

The place of the little-studied regime of "branching jets" in the general phenomenological classification is determined. It turned out that the "branching jets" mode is realized only for very large dimensionless liquid viscosities (in the region of transition from a dimensionless very viscous liquid to a dimensionles viscoelastic liquid), high electrical conductivity of the liquid, with a violation of the axisymmetry of the jet at the final stage of the phenomenon. The intensity of the electrostatic field in the vicinity of the daughter jets during the implementation of the "branching jets" mode is at the threshold of ignition in the surrounding gas environment corona discharge. It is shown that the "branching jet" and "fan" dispersion modes differ in the electrical voltage applied to the discharge gap and in the viscosity of the liquid being dispersed.