Mixtures of Polyacrylic Acid and Nonionic Surfactants at the Water/Air Interface

Abstract

The present work reports on aqueous solutions of the nonionic surfactant octaethylenglycol monododecyl ether and polyacrylic acid. By combining surface tension measurements with ellipsometry, supplementary results could be received on the surface layer of the aqueous solutions. At pH ⩾ 8, no interactions occur and the adsorbed film is essentially a surfactant layer. At pH = 3 and above the critical micelle concentration of the surfactant/polymer mixture, the surface tension is higher and the adsorbed layer much thicker than in the case of the pure surfactant solution, i.e., the surfactant film is modified by the presence of polyacrylic acid. This can be explained by the adsorption of polyacrylic acid into the interfacial surfactant layer, induced by H-bonding between polyacrylic acid and ethylenglycol units of the surfactant head group.