Polymer brushes are of great technological interest for biochemical, biophysical, and biomedical applications owing to their stimuli-responsive behavior on changes in temperature, pH, or solvent. Mixed brushes, containing at least two different polymers, are of particular interest, since they can represent biofunctional surfaces for controlled protein/cell adsorption.One important temperature-sensitive polymer is poly(N-isopropyl-acrylamide) [PNIPAAm]. It swells/deswells around its lower critical solution temperature of 32�C. In order to understand the protein ad-/desorption process in mixed PNIPAAm brushes, one needs an extended understanding of this swelling behavior.For this, infrared spectroscopic ellipsometry is employed for studying the film properties at the solid-liquid interface. A 12.6 nm thin PNIPAAm brush is investigated in Millipore� water in-situ at different temperatures around 32�C. An attempt is made to quantitatively describe the swelling behavior using optical-model calculations and to extract swollen brush thickness, water content, and vibrational-band shifts corresponding to structural changes.

Temperature-sensitive swelling behavior of thin poly(N-isopropylacrylamide) brushes studied by in situ infrared spectroscopic ellipsometry

244th National Meeting (2012)

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