Ostwald Ripening of Alkane Emulsions Stabilized by Polyethylene Glycol Monolaurate

Abstract

The Ostwald ripening of alkane in water emulsions stabilized by the surfactant poly(ethylene glycol) monolaurate (PEM) was investigated. Surprisingly the measured ripening rates were significantly below the rate which can be predicted by the Lifshitz−Slyozov−Wagner (LSW) theory and decreased in the presence of surfactant micelles. A possible explanation of the effect of these micelles is that they withdraw oil from the continuous phase and hence slow the transport of oil from smaller to larger droplets.

Oil-in-water nanoemulsions for pesticide formulations

“…It is shown that the slope declines with the decreasing R os , which means the more stable nanoemulsions are obtained with higher surfactant concentration. This phenomenon is consistent with results reported earlier [35][36][37]. It was suggested that excess micelles formed in the aqueous phase, which act a solubilization sites for added oil.…”

Formation and stability of paraffin oil-in-water nano-emulsions prepared by the emulsion inversion point method

“…This treatment will yield the Ostwald ripening rate in the presence of micelles, predicting a remarkable increase of the rates [18,19]. However, Smet et al [27] and Hoang et al [28] observed a reduced ripening rate with increasing surfactant concentration. They argued that the oil solubilized in the micelles was not dispersed at the molecular level in the continuous phase.…”

Influence of surfactant structure on the contribution of micelles to Ostwald ripening in oil-in-water emulsions

“…The equilibrium solubility of oil in micelles, c eq mic , is several orders of magnitude higher than the molecular solubility c eq w of the oil. Yet the enhancement in experimentally measured Ostwald ripening rates, x E , in the presence of micelles, relative to that in their absence, is found to be much weaker than expected based on this solubility increase [7][8][9][10][11][12][13]. Furthermore, studies of systems containing ionic surfactants found that x E was virtually independent of surfactant concentration, leading researchers to conclude that there is no contribution from anionic micelles to the ripening mechanism [7,9,10].…”