Adsorption of hydrophobically modified polyacrylic acid on a hydrophobic surface : hysteresis caused by an electrostatic adsorption barrier

J.G. Göbel, N.A.M. Besseling, M.A. Cohen Stuart, C. Poncet

Research output: Contribution to journalArticleAcademicpeer-review

37 Citations (Scopus)

Abstract

The adsorption of hydrophobically modified polyacrylic acid (HM-PAAc) has been compared to the adsorption of unmodified polymers by means of reflectometry. The polymers were adsorbed onto a noncharged hydrophobic polystyrene surface. The adsorption kinetics of both types of polymer is the same until a certain surface coverage. Then the unmodified sample shows a saturation while the hydrophobically modified polyacrylic acid continues to adsorb. The adsorption behavior of the polyelectrolyte can be controlled by the pH and the ionic strength of the solution. For ionic strengths of 0.001MNaCl the hydrophobically modified polymer shows a larger adsorbed amount at pH 3 to 4 compared to the unmodified polymer. At pH higher than 4 the differences are less significant. At higher ionic strength the amount of adsorbed material increases for both polymers. While doing adsorption–desorption cycles a hysteresis-effect was detected. At the same pH the hydrophobically modified polymer sticks to the surface while the unmodified polymer is already desorbing completely. The hysteresis vanishes when the ionic strength of the solution is increased.
Original languageEnglish
Pages (from-to)129-135
JournalJournal of Colloid and Interface Science
Volume209
DOIs
Publication statusPublished - 1999

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