Kinetics of Adsorption Layer Formation in Solutions of Polyacid/Surfactant Complexes

The dynamic dilational elasticity of adsorption layers of the complexes between polyacids and dodecyltrimethyl ammonium bromide were measured by the oscillating ring method as a function of surface age and surfactant concentration. The concentration dependencies of surface tension and dilational surface elasticity are similar to the corresponding dependencies of other polyelectrolyte/surfactant solutions. At the same time, the kinetic dependencies of the dynamic surface elasticity differ significantly from the results for other systems and exhibit in respective concentration ranges one or two local maxima. The first maximum and the associated distortion of the harmonical surface tension oscillations are caused by an aggregate formation in the surface layer. The second maximum occurs simultaneously with a multilayer formation at the liquid surface, which probably results in a new relaxation mechanism of surface stresses. The hydrophobic interactions influence the height and position of the second elasticity maximum, which is more pronounced for complexes of DTAB with the more hydrophobic polymethacrylic acid as compared to the poly(acrylic acid), and the surface tension values in the plateau region.