A density depletion model for the interfacial tension between immiscible liquids

• Contact angle patterns are described by a model for liquid density depletion.
• The same model can be extended to describe liquid–liquid interfacial tensions.
• Deviation of data from the model increases with mutual solubility of liquids.

A simple model for density depletion of organic liquid molecules at an interface with a lower-energy solid is revised. The model is then extended to immiscible liquid–liquid systems and used to develop a relationship between the surface tensions of pure liquids and the interfacial tension between them. Calculations are compared to literature data for contact angles and interfacial tensions, and the effect of partial miscibility between liquids on their interfacial tension is examined.

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