Authors Abraham, T. ; Giasson, S. ; Gohy, J.F. ; Jérome, R. ; Müller, B. ; Stamm, M.
Title Adsorption Kinetics of a Hydrophobic-Hydrophilic Diblock Polyelectrolyte at the Solid-Aqueous Solution Interface: A Slow Birth and Fast Growth Process
Date 01.09.2000
Number 9402
Abstract The adsorption kinetics of a diblock copolymer poly(<I>tert</I>-butyl methacrylate)-<I>b</I>-poly(glycidylmethacrylate sodium sulfonate) on hydrophobic substrate from aqueous solution under different addedmonovalent salt (NaCl) concentrations was investigated using an ellipsometric technique. The effect ofmonovalent counterion size on adsorption kinetics of the same copolymer on hydrophobic surfaces wasalso part of the investigation. The results, in general, indicate that the adsorption process on solid surfacesoccurs through the anchoring of hydrophobic chains due to the short-ranged hydrophobic interactions.The kinetic data reveal three distinct stages in the adsorption process: an incubation period, a subsequentfast growth process of the polymer layer, and a plateau (equilibrium) region. These three stages arefound to be influenced by salt concentration as well as counterion size. The equilibrium adsorption densityincreases as a function of salt concentration, and the dependence is found to be different from thetheoretical predictions. The incubation time increases with salt concentration according to a power lawdependence, and a simple bound ionic layer formation on the substrate is proposed as a possi<br />bleexplanation for this observation. An attempt has been made to explain the growth process in terms of anAvrami type ordering process. The Avrami analysis indicates that the buildup of polyelectrolyte layerstructure depends on added salt conditions. Our kinetic data suggest that the diffusion of the chains tothe surface is not the rate-controlling process for adsorption. A slow birth (nucleation) and fast growthof the layer seem to be the determining adsorption process.
Publisher Macromolecules
Citation Macromolecules 33 (2000) 6051-6059
Tags block-copolymers ionic-strength brushes solvent silica micellization ellipsometry monolayers surface layer

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