Effect of Surface Elasticity on Ostwald Ripening in Emulsions

Abstract

The coarsening of droplets in an emulsion with a size distribution that initially is given by the Lifshitz−Slyozov−Wagner (LSW) distribution is studied by means of numerical calculations taking into account elastic interfacial behavior. Droplets smaller than the critical radius will shrink while droplets larger than the critical radius will grow. For a zero interfacial elasticity the stationary LSW distribution is obtained and its coarsening rate matches theoretical values. The critical droplet radius, number-averaged droplet radius, and volume-surface-averaged droplet radius increase with time. Low interfacial elasticity with respect to initial interfacial tension causes the initial LSW distribution to become bimodal. The size distribution of the coarsening peak can still be described by the LSW distribution. The smaller peak that accumulates in time has an average radius that depends on the ratio between the interfacial elastic modulus and the interfacial tension. For large ratios (E/σ > 1), the system goes within a short time to a stable situation without changes in particle size with time.

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