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Motornov, M. ; Minko, S. ; Eichhorn, K.-J. ; Nitschke, M. ; Simon, ; Stamm, M.
Reversible Tuning of Wetting Behavior of Polymer Surface with Responsive Polymer Brushes

We develop the route to fabricate mixed brushlike layers on polyamide substrates (PA-6, PA-6I, PA-66)by the "grafting from" approach. The PA substrates were functionalized by NH3 plasma. The azo initiatorof radical polymerization was covalently bound to the functionalized PA surface. A two-step graftingprocedure was applied to graft polystyrene in the first step and poly(2-vinylpyridine) in the second step.We found remarkable differences between grafting on Si wafers and on the PA substrates. "Grafting from"the PA surface results in a dramatic increase of the surface roughness of the film which can be explainedby grafting in a swollen surface layer of PA. Because of this effect, we found a substantial amount of graftedpolymers even on not functionalized PA substrates, which was explained by grafting via chain transferreaction. The synthesized mixed polymer brushes form responsive coatings which switch their morphologydue to the interplay between lateral and vertical phase segregation upon exposure to selective solvent.The switching of morphology affects the change of the surface composition of the brushes and their surfaceenergetic state. We performed the same grafting procedure on the surface of PA fabric. In this case theswitching behavior was amplified by the texture of the material: wettability of the fabric with the mixedbrush was switched from complete wetting to highly hydrophobic state (150 water contact angle).

Langmuir 19



September 2003


Polymer Interfaces