Kavli Affiliate: Jos Zwanikken

| First 5 Authors: Markus Bier, Joost de Graaf, Jos Zwanikken, Rene van Roij,

| Summary:

The interfacial tension of a liquid droplet surrounded by another liquid in

the presence of microscopic ions is studied as a function of the droplet

radius. An analytical expression for the interfacial tension is obtained within

a linear Poisson-Boltzmann theory and compared with numerical results from

non-linear Poisson-Boltzmann theory. The excess liquid-liquid interfacial

tension with respect to the pure, salt-free liquid-liquid interfacial tension

is found to decompose into a curvature-independent part due to short-ranged

interfacial effects and a curvature-dependent electrostatic contribution.

Several curvature-dependent regimes of different scaling of the electrostatic

excess interfacial tension are identified. Symmetry relations of the

interfacial tension upon swapping droplet and bulk liquid are found to hold in

the low-curvature limit, which, e.g., lead to a sign change of the excess

Tolman length. For some systems a low-curvature expansion up to second order

turns out to be applicable if and only if the droplet size exceeds the Debye

screening length in the droplet, independent of the Debye length in the bulk.

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