Phase equilibrium and thermodynamic properties in microemulsions

A calorimetric investigation was performed on the partition of n-pentanol in the external oil phase and in the interfacial layer of the water-in-oil microemulsion system sodium dodecyl-benzenesulfonate(DDBS)/n-pentanol/n-heptane/water. The results show that fine changes can be observed in the structure of the water-in-oil emulsion and microemulsion droplets, such as the n-pentanol/DDBS mole ratio increase in the interfacial layer; further, the alcohol/surfactant mole ratio a in the interfacial layer of the droplets, and also the standard thermodynamic functions of the alcohol transition from the external phase to the interfacial phase (Delta G(e-->s)(o), Delta H-c-->s(o) and Delta S-e-->s(o)), can be derived from calorimetric data.