Solvent effect on the adsorption of 1-octadecanol at oil/water interface

In order to study the effect of solvent on the adsorption at interfaces, interfacial tension was measured as a function of temperature and compositon for the systems of water and solutions of 1-octadecanol in cyclohexane, cyclo-hexene, mesitylene, toluene, and benzene. The interfacial density of 1-octadecanol and the entropy and energy of interface formation were calculated thermodynamically. It was found that cyclohexane causes a significant adsorption of 1-octadecanol and marked decreases in the entropy and energy changes, giving rise to phase transition from expanded to condensed film, while benzene, toluene, and mesitylene cause only a slight adsorption and small decrease in thermodynamic quantities. Gyclohexene was found to give rise to an intermediate adsorptive behavior of 1-octadecanol. The results were interpreted in terms of the mutual solubility between water and solvents and that of 1-octadecanol in the solvents.