Ostwald ripening in emulsions: estimation of solution thermodynamics of the disperse phase.
The rate of Ostwald ripening has been measured for small emulsions prepared by the dilution of O/W microemulsions containing a range of n-alkanes. The rates were determined as a function of temperature for decane, undecane, dodecane and tri-decane using photon correlation spectroscopy. The aqueous solubilities of these oils were estimated from the rates of ripening using the Lifshitz, Slyozov and Wagner theory of Ostwald ripening. These solubilities were used to calculate the free energy, enthalpy and entropy of solution for the 4 alkanes. Values obtained were in good agreement with literature values. The free energy of solution of hexadecane and octadecane were also determined from the rate of ripening of mixed oil phase emulsions with dodecane using the treatment suggested by Kabalnov. The values obtained agreed well with extrapolated values of the free energy from lower alkanes, suggesting that coiling or aggregation of the longer chain molecules in solution was not affecting the solubility.
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Syngenta Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK.