arXiv subjects

Alexey Kabalnov

Publications and source records attributed to Alexey Kabalnov.

4 recordsLinked to original sources

arXiv2026

Ostwald ripening controlled by diffusion of a sparingly soluble component

Additives of sparingly soluble components are known to slow down or completely inhibit Ostwald ripening in dispersed systems. In this paper, our earlier model of stabilization against Ostwald ripening is revisited and extended. In a quasi-steady-state mode, the process is shown to be controlled by the diffusion of the less soluble component, and the whole machinery of the classical Lifshits-Slezov-Wagner (LSW) theory can be leveraged almost without any change. The particle size distribution is predicted to follow the same distribution function pattern as in the classic LSW theory. The rate of ripening follows the classic cubic law. To extend our earlier result, an improved extrapolatory equation for the ripening rate is derived, that covers the whole formulation range, accounts for the difference in molar volumes of the components and for the solution non-ideality. The behavior described above is observed over the range of high concentrations of the poorly soluble component, with the cutoff determined by the lock-in number described in the previous paper of this series. When the concentration of the additive is low, the kinetics no longer follows the LSW pattern; instead, the particle size distribution becomes bimodal, with the fraction of 'fines' enriched by the poorly soluble component and the fraction of the large particles to ripen as if no additive were present. The lock-in parameter L1 can be used to characterize for the transition from one mode to another. In the end, some practical stabilization approaches for emulsions are discussed.

cond-mat.soft↗

arXiv2026

Dissolution of a two-component drop onto macrophase due to surface tension effect

Additives of sparingly soluble components are known to slow down or completely inhibit Ostwald ripening in dispersed systems. In this paper series, our earlier model of the stabilization against Ostwald ripening is revisited and extended over the whole range of compositions, molar volumes of components, and their activity coefficients. In the first paper, a simpler problem, the dissolution of a two-component drop under the action of excess Laplace pressure inside is analyzed. Three stages of dissolution are identified. In the first stage, called pre-lock-in, the concentration of the poorly soluble component undergoes a quick increase, and the system enters the lock-in state, in which the Laplace pressure effect on the chemical potential of the more soluble component is nearly completely counterbalanced by the Raoult effect. After this, the dissolution kinetics slows down and enters a steady state. In the process, the concentration of the sparingly soluble component continues to increase, first slowly and then more rapidly in the very end of the particle lifetime; this latter stage is called the 'late lock-in'. Despite all those variations, if the initial concentration of the poorly soluble component is above a certain threshold, the dissolution kinetics nearly follows the classical cubic law. An improved equation for the rate of dissolution is proposed that covers the whole formulation range and represents an extension over our previous formula.

cond-mat.soft↗

arXiv2026

Solubilization kinetics of oils by ionic and nonionic micelles: theoretical model

Experimental data on solubilization kinetics found in literature were analyzed by using the model proposed earlier (1). The rates of oil molecular exchange between the micellar core and the surrounding aqueous solution were determined. It was concluded that the solubilization of hydrocarbon molecules by nonionic surfactants of ethylene oxide type is essentially barrier-free, that is, is diffusion controlled. It is quite different for ionic surfactants, where the rate is one-two orders of magnitude slower, indicating the existence of a potential barrier for hydrocarbons to get inside the micelles. A Fickean diffusion model of solubilization has been proposed to explain these trends. For ionic micelles, the hydrocarbons are predicted to be excluded from the micellar double layer region because of their low dielectric constant. The Poisson-Boltzmann model was used to model this effect; the diffusion retardation factors were compared with the experiment and a fair agreement was seen. For nonionic groups, such as oligoethylene oxide, on the other hand, no such barrier was predicted to exist. The analysis of this paper is performed only for the case of the 'slow' solubilization; it does not cover the case of the rapid, 'catastrophic' solubilization observed in the other group of experiments; the distinction between the slow and fast mechanisms is discussed and a possible explanation is suggested.

cond-mat.soft↗

arXiv2026

Micellar effects on Ostwald ripening in emulsions: Transition from cubic to quadratic particle size growth

Ostwald ripening in O/W emulsions in presence of solubilizing micelles is theoretically studied. At small average sizes, the kinetics is predicted to follow the classical Lifshits-Slezov-Wagner cubic law, with the rate proportional to the molecular solubility of the oil in water, as if no micelles were present. At larger particle sizes the kinetics transitions to the Wagner's quadratic law. The crossover point for the kinetics depends on the dynamics of the oil solubilizate-micelle exchange; it is set by the value of the oil atmosphere distribution parameter, kappa, which, somewhat like Debye length, is proportional to the square root of the micellar concentration. It should be noted that in the range when 1/kappa is close to the particle average radius, the ripening kinetics still nearly follows the cubic law, with only moderate deviations; in this case, the micellar effects are experimentally seen not as the deviations from the linearity, but as an apparent increase in the cubic rate. The increase is predicted to be larger in case of nonionic micelles of ethylene oxide type compared to ionic ones.

cond-mat.soft↗