Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 40512
Title Forces between polymer-covered surfaces: a colloidal probe study.
Author(s) Giesbers, M.; Kleijn, J.M.; Fleer, G.J.; Cohen Stuart, M.A.
Source Colloids and Surfaces. A: Physicochemical and Engineering Aspects 142 (1998). - ISSN 0927-7757 - p. 343 - 353.
Department(s) Physical Chemistry and Colloid Science
Publication type Refereed Article in a scientific journal
Publication year 1998
Abstract An atomic force microscope was used to measure the interaction forces between a polymer-covered silica sphere and a polymer-covered silica plate at various pH values and electrolyte concentrations and for different polymer chain lengths. The polymer used was poly(ethylene oxide) (PEO). The force measurements were performed in aqueous solution without dissolved polymer, at scan rates corresponding to the velocity of Brownian collisions between dispersed colloidal particles. In all cases the repulsion on approach was found to be electrostatic in nature: although the PEO adsorption layers are saturated, there is no sign of steric repulsion before the distance of closest approach between the silica surfaces is reached. At pH 4 the approach curves show, for separations smaller than 20 nm, an attractive component which partly compensates the electrostatic repulsion. On retraction a strong adhesion is observed, which is attributed to bridging. At pH 8 and low electrolyte concentration (10−3 M NaCl) the interaction is repulsive on approach and on retraction: no adhesion by bridging takes place. However, upon increasing the NaCl concentration a weak adhesion is induced. At neutral pH (~6.5) the adhesion on separation depends on the force with which the surfaces have been pressed together (10−3 M NaCl). The pH dependence of the interaction curves is discussed in terms of the segmental adsorption energy, which is known to decrease with increasing pH. Measurements at pH 4 show a strong dependence of the adhesion force on the chain length. A linear relationship between the adhesion force and the surface coverage (in mass per unit area) is found.
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