Individual and Collective Behavior of Emulsion Droplets Undergoing Ostwald Ripening.

Ostwald ripening (OR) is the dominating phase separation mechanism in nanoemulsions consisting of the mass exchange between separated droplets by dissolution and absorption of molecules. Here, we propose a model based on a stochastic equation for the mass exchange coupled to a Brownian dynamics algorithm. Our model accounts for the simultaneous gain and loss of mass within a medium, where the presence of sources and sinks leads to a complex distribution of dissolved oil molecules. Also, a criterion for possible nucleation zones based on the definition of a saturation area around the droplets is found. The predictions of the collective behavior are constructed on the individual contributions of each droplet with its own environment. Individual droplets undergoing molecular exchange exhibited anomalous diffusion, whereas when performing the collective analysis, such a behavior was disguised. We used reported experiments under diverse conditions to validate and test the scope of our model, including the modification to the interfacial tension via Gibbs elasticity, finding close agreements. Our results imply that saturation is not conditional for the occurrence of OR. The ability of this model to extend the limitations imposed by traditional treatments to a broader number of physicochemical conditions makes it a useful complementary tool for predicting and understanding experimental results of emulsions experiencing OR.