Adsorption of Dimethyl Sulfoxide to the Liquid/Vapor Interface of Water and the Thermochemistry of Transport across the Interface

Resonantly enhanced surface second harmonic generation has been used to measure the adsorption isotherm of dimethyl sulfoxide (DMSO) at the liquid/vapor interface of water. The Langmuir model of interfacial adsorption was used to model the data allowing determination of −11.8 (σ = 1.2) kJ/mol for the Gibbs free energy of adsorption of DMSO to the liquid/vapor interface of water at 293 K. This value of the adsorption energy is combined with data obtained from the literature to yield a complete thermodynamic characterization of a model potential energy surface for the transport of DMSO across the liquid/vapor interface of water. Some implications of this potential energy surface on the kinetics of mass transport are presented.