Thermodynamics of reversible adsorption of amphiphiles from solution onto interface near saturation.

Based on the fundamental thermodynamical relations for surface phases given by Guggenheim and the rigorous discussions by Vochten, Petre, and Defay, the reversible entropy and enthalpy differences for the amphiphile molecules in between the adsorbed surface and the bulk phases of solution were derived and calculated respectively. The entropy of the amphiphile solutes at the interface is lower than that in the bulk when the adsorption is below saturation. However, when the adsorption approaches saturation the entropy difference becomes either zero or positive. These features can be reasonably explained by the adsorption-orientation effect of the amphiphile solute molecules in the interfacial adsorbed layer. [ABSTRACT FROM AUTHOR]