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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.87: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

Reversible Temperature Induced Switching of Grafted Poly-N-isopropylacrylamide Brushes — •Petra Uhlmann, Eva Herold, Sina Burkert, Martin Müller, and Manfred Stamm — Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden

Polymer brushes, as linear polymer chains tethered by one end to a solid surface with sufficient grafting density, represent a special case of grafted polymer thin films and a versatile tool to control and switch the properties of polymer interfaces. Poly-N-isopropylacrylamide (PNiPAAM) which is known to undergo conformational changes due to temperature alterations (stretched below and coiled above the lower critical solution temperature (LCST) of 32°C) represents a very interesting mean to reversibly switch the physico-chemical properties of polymer interfaces when immobilized in a brush-like conformation at solid interfaces. The switching process and mechanism of collaborative acting PNiPAAM brushes was investigated using ellipsometry, dynamic contact angles and attenuated total reflectance infrared spectroscopy (ATR). The phase transition mechanism of the PNiPAAM brushes observed near the LCST was found to be independent of the molecular weight of the polymer. Using ATR-FTIR the formation of internal hydrogen bonds due to switching, by ellipsometry the deswelling of the brush in aqueous environment above the LCST and by wetting measurements changing hydrophilicity in dependence of temperature could be followed. The influence of molecular weight and grafting density on switching process and mechanism will be discussed.