Controlling the adsorbed conformation and desorption of polyelectrolyte with added surfactant via the adsorption mechanism: A direct force measurement study

George Maurdev, Michelle L. Gee, Laurence Meagher

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11 Citations (Scopus)


When complexed PSS/CTAB is coadsorbed onto silica, a long-range, predominantly electrosteric repulsion is measured which decays exponentially with surface separation. Adsorption is driven by locally hydrophobic, surfactant-rich regions along the PSS chain. These anchor the PSS chain to the surface, resulting in a classical loop and tail adsorbed conformation. An increase in pH results in an increase in electrostatic repulsion between the silica surface and PSS, which drives an initially rapid desorption of some of the PSS/CTAB complex. Any remaining PSS/CTAB desorbs via a slow unravelling, as points of attachment to the surface are broken over time, allowing the PSS to extend further into solution. This continues until desorption is complete after 66 h. In contrast, adsorption of the PSS/CTAB complex onto a preadsorbed CTAB layer leads to a less extended, more compact surface layer since now adsorption is driven not only by the hydrophobic surfactant-rich regions along the PSS chain but also by a hydrophobic attraction between the PSS backbone and any adsorbed CTAB. An increase in pH results in rearrangement of the PSS/CTAB complex to a more extended conformation since now there is more segment-segment and surface-segment repulsion. This is evidenced by the increase in the range of the net repulsion and the fact that the repulsion now decays exponentially in a manner similar to that obtained when PSS/CTAB is able to loop and tail into solution. More points of attachment must be broken to achieve complete desorption of the PSS/CTAB complex, and hence complete desorption is kinetically hindered.

Original languageEnglish
Pages (from-to)9401-9408
Number of pages8
Issue number24
Publication statusPublished - 26 Nov 2002
Externally publishedYes

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