Wetting properties of Saponaria officinalis saponins

Abstract

The contact angles of water, formamide and diiodomethane on the polytetrafluoroethylene (PTFE), poly(methyl methacrylate) (PMMA) and quartz covered with Saponaria officinalis saponins and pure hederagenin films as well as the contact angles of aqueous solutions of saponins on the PTFE, PMMA and quartz surface, were measured. The adsorption of the saponins at the solid-water interface was also compared to that at the water-air one. The possibility to adsorb the saponins at the solid-water interface was analyzed on the basis of the Gibbs standard free energy of adsorption relative to the Gibbs free energy of interactions of saponins molecule with solid surface through the water phase. The changes in the solid-water and water-air interface tension under the influence of saponins adsorption were considered in the light of the PTFE, PMMA and quartz wettability by the aqueous solution of saponins. From this consideration it results that the contact angle of aqueous solution of saponins on PTFE, PMMA and quartz surface as well as the adhesion work of these solutions to solid can be predicted on the basis of the components and parameters of the water, solid and solution surface tensions. Experiments indicated that saponins are poor wetting agents and the adhesion work of the saponins solution does not depend on their concentration.