Ostwald Ripening in Emulsions Containing Two Disperse Phase Components

1 Ostwald Ripening in Emulsions Containing Two Disperse Phase Components 

To counteract emulsion growth via Ostwald ripening, Higuchi and Misra proposed the addition of a second disperse phase component which is insoluble in the continuous phase. In this case, significant partitioning between different droplets is predicted, with the component having low solubility in the continuous 

The equilibrium determined by eqn. (9.9) is stable if the derivative of dAnJdr is greater than zero for all droplets in a polydisperse system. Based on this the following stability criterion was derived by Kabalnov et alf  

Weers and Arlauskas utilized sedimentation field-flow fiactionation (SdFFF) 

In two other studies the predicted evolution of a bimodal particle size distribution was examined. Kabalnov e( al. examined hexane-in-water emulsions stabilized by varying levels of hexadecane (A 02 = 0.1, 0.01, 0.001). For the higher mole fractions, the emulsion growth rates were reliably predicted by eqn. (9.11). Also, these emulsions had a physical appearance identical to that of an emulsion containing only hexadecane, i.e. they did not cream. The = 0.001 sample behaved quite differently, however. Upon storage, this emulsion quickly separated into two layers a sedimented layer with a droplet size of ca. 5 pm and a dispersed population of submicron droplets (i.e. a bimodal distribution). The 5 pm droplets were equivalent to the droplet size observed for a fresh perfiuorohexane emulsion prepared under similar conditions. In light of the fact that the stability criterion was not met for this mole fraction of hexadecane, the observed bimodal distribution of droplets is predictable. A bimodal size distribution was also observed by the SdFFF technique by Weers and Arlauskas in PFOB-in-water emulsions stabilized by low levels of PFDB. 

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