Dynamic Light Scattering Studies on Ostwald Ripening and Composition Ripening of Oil Droplets in Oil-in-Water Emulsion Systems

Dynamic light scattering studies on Ostwald ripening and composition ripening were performed in n-decane-in-water emulsion and squalane-in-water emulsion. Ostwald ripening was observed in n-decane-in-water emulsion, in which smaller droplets were more significant than larger droplets because of higher solubility of smaller droplets. When smaller droplets presence with larger droplets in emulsion, Ostwald ripening of larger droplets was enhanced, indicating that higher solubility of smaller droplets led to Ostwald ripening. Composition ripening was observed after mixing an n-decane-in-water emulsion and an squalane-in-water emulsion. Size decrease of n-decane droplets was always observed even though size of squalane droplets was smaller than that of n-decane droplets. Namely, n-decane molecules always diffuse from n-decane droplets into squalane droplets due to relatively high solubility of n-decane in water than that of squalane. These findings suggest that composition ripening more significantly contributes to droplet growth than Ostwald ripening (size dependent does).