Interactions between droplets in immiscible liquid suspensions and the influence of surfactants

Fuente: arXiv
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Autores principales: Archer, A. J., Sibley, D. N., Goddard, B. D.
Formato: Preprint
Publicado: 2025
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author Archer, A. J.
Sibley, D. N.
Goddard, B. D.
author_facet Archer, A. J.
Sibley, D. N.
Goddard, B. D.
contents We develop a general method for determining the effective interaction potential between two or more droplets suspended within a fluid phase. Our approach is based on classical density functional theory. Here, we apply the method to determine the interaction potential between oil droplets suspended in water and also consider the influence of adding a third species, alcohol. This ternary mixture is that found in the ouzo beverage. The ouzo system exhibits spontaneous emulsification when the neat spirit is mixed with water. The oil emulsion that forms has been observed to be surprisingly long-lived. Here we show that the alcohol in the system does indeed play a role in making the droplets more stable, by decreasing the oil-water interfacial tension and therefore also the strength of the attractive interactions between droplets. Within our theory, the surfactant nature of the alcohol can be enhanced without changing the bulk fluid thermodynamics. In fact, our theory can be used to model surfactant mixtures. In this model, the effective interaction between pairs of oil droplets can become repulsive, with a free-energy barrier to droplets merging, thus making them stable.
format Preprint
id arxiv_https___arxiv_org_abs_2512_14380
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Interactions between droplets in immiscible liquid suspensions and the influence of surfactants
Archer, A. J.
Sibley, D. N.
Goddard, B. D.
Soft Condensed Matter
Statistical Mechanics
We develop a general method for determining the effective interaction potential between two or more droplets suspended within a fluid phase. Our approach is based on classical density functional theory. Here, we apply the method to determine the interaction potential between oil droplets suspended in water and also consider the influence of adding a third species, alcohol. This ternary mixture is that found in the ouzo beverage. The ouzo system exhibits spontaneous emulsification when the neat spirit is mixed with water. The oil emulsion that forms has been observed to be surprisingly long-lived. Here we show that the alcohol in the system does indeed play a role in making the droplets more stable, by decreasing the oil-water interfacial tension and therefore also the strength of the attractive interactions between droplets. Within our theory, the surfactant nature of the alcohol can be enhanced without changing the bulk fluid thermodynamics. In fact, our theory can be used to model surfactant mixtures. In this model, the effective interaction between pairs of oil droplets can become repulsive, with a free-energy barrier to droplets merging, thus making them stable.
title Interactions between droplets in immiscible liquid suspensions and the influence of surfactants
topic Soft Condensed Matter
Statistical Mechanics
url https://arxiv.org/abs/2512.14380