Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 13: Solid / liquid interfaces I

O 13.8: Talk

Monday, March 14, 2011, 16:45–17:00, WIL B321

Probing the intrinsic switching kinetics of thermoresponsive polymer brushes at the water/substrate interface — Crispin Amiri Naini, Steffen Franzka, Sven Frost, Mathias Ulbricht, and •Nils Hartmann — Fakultät für Chemie, CeNIDE, NETZ, Universität Duisburg-Essen, Universitätsstr. 5, 45141 Essen

Stimuli-responsive polymers are widely used as actuators and sensors in a variety of applications including adaptive microoptics, microfluidic chips and smart membranes. A detailed knowledge of the intrinsic switching kinetics of such materials is of key importance. Here we demonstrate a stroboscopic photothermal laser manipulation technique, which allows for real-time observation of the switching behavior of poly-n-isopropylacrylamide brushes at the water/substrate interface. A modulated beam of a microfocused laser is used to intermittently heat the substrate surface and locally trigger swelling and deswelling of the thermoresponsive polymer film. Spatial variations of the swelling ratio are monitored using reflectometric interference video microscopy. This facilitates direct parallel measurement of the temperature-dependent switching kinetics of brush layers with thicknesses below one hundred nanometers. Response times range from the millisecond down to the microsecond range demonstrating the prospects of surface-grafted polymer films in fabrication of nanosized polymeric actuators and sensors with fast responsivities.

[1] M. Mathieu, A. Friebe, S. Franzka, M. Ulbricht, N. Hartmann, Langmuir 25 (2009) 12393.