Competitive adsorption between non-ionic polymers and surfactants on silica

The competitive adsorption on silica between non-ionic surfactants of the alkylphenol poly(ethylene oxide) type and neutral polymers of the poly(ethylene oxide) type has been investigated as a function of polymer chain length by determining adsorption isotherms of 50:50 wt.% mixtures. For molecular weights of the polymer below 10 000 g mol(-1), surfactant adsorption at saturation is not affected by the presence of the polymer. For higher molecular weights, polymer molecules are preferentially adsorbed at low concentrations, whereas at higher concentrations the behaviour of these systems can be characterized by a threshold molecular-weight value, above which the polymer displaces the surfactant. The results are interpreted by the competition between two types of macromolecules: the adsorbed polymer and the surfactant surface aggregate. (C) 1997 Elsevier Science B.V.