title: Competitive adsorption of nonionic surfactant and nonionic polymer on silica.
abstract: Competitive adsorption of the nonionic polymer poly(ethylene oxide) (PEO) and the nonionic surfactant of the type poly(ethylene oxide) alkyl ether from aqueous solutions on a silica surface is examined. From one-component solutions, both species readily adsorb onto silica and, in the bulk of mixed (two-component) solutions, polymer-surfactant complexes are not observed. Because both species bind by the same mechanism to silica, subtle differences in layer structure, or other species-specific parameters, determine whether one or both of the species will adsorb. It was found that various surfactants can displace PEO up to a certain critical molecular weight. Surfactants with a high aggregation number, in bulk and on the surface, can displace PEO with a higher molar mass than surfactants with a low aggregation number. As the molar mass of the polymer increases, the time a surfactant needs to completely displace the polymer increases. We can explain both the existence of the critical molar mass and the decrease in adsorption kinetics with a shift in the critical surface association concentration (CSAC).
authors.affiliation: Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands. bart.postmus@ wur.nl
authors.forename: Bart R
authors.initials: BR
authors.lastname: Postmus
authors.forename: Frans A M
authors.initials: FA
authors.lastname: Leermakers
authors.forename: Luuk K
authors.initials: LK
authors.lastname: Koopal
authors.forename: Martien A Cohen
authors.initials: MA
authors.lastname: Stuart