Effect of temperature on the enthalpies of formation of water-o-xylene-Triton X-100 microemulsions

Enthalpies of solution for water-o-xylene-Triton X-100 (TX-100) microemulsions and their components in 2-propanol are determined thermochemically at 288.15, 298.15, and 313.15 K. Enthalpies of formation for the microemulsions are calculated using a thermochemical cycle. It is shown that the enthalpies of formation are negative and fall in moving from water/oil microemulsions to oil/water microemulsions. The obtained data show that strong molecular interactions between components in the investigated systems favor the formation of thermodynamically stable microemulsions. It is concluded that the spontaneous formation of the microemulsions can be due to both the entropy and enthalpy contributions to the change in free energy.