Properties of n-octyl-β-d-glucopyranoside and sodium dodecylsulfate mixed monolayer at the water-air interface

Abstract

The measurements of the surface tension of the aqueous solution of n-octyl-β-d-glucopyranoside (OGP) and sodium dodecylsulfate (SDDS) mixtures were performed. From the obtained results the composition and density of the mixed surface layer, standard Gibbs free energy of adsorption and Gibbs free energy of the OGP and SDDS mixing in the surface layer were determined. These parameters were discussed based on the size of OGP and SDDS molecules as well as their contactable area at perpendicular and parallel orientations. These parameters were also discussed with regard to SDDS-SDDS, OGP-OGP and SDDS-OGP Gibbs free energy of interactions through the water phase. These interactions were determined on the basis of the components and parameters of the hydrophobic and hydrophilic parts of the surfactants molecules. Their values were compared to the parameter of the interactions between the SDDS and OGP molecules in the surface layer at the water-air interface. The negative values of this parameter suggest that there is the synergistic effect in the reduction of water surface tension by the OGP and SDDS mixture.