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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Focus: Amphiphilic systems III

CPP 3.3: Vortrag

Montag, 23. März 2009, 18:45–19:00, ZEU 222

Temperature dependent swelling and switching kinetics of gold coated end-capped PNIPAM thin films — •Weinan Wang¹, Jan Perlich¹, Gunar Kaune¹, Achille M. Bivigou Koumba², Andre Laschewsky², Christine M. Papadakis¹, Robert Cubitt³, and Peter Müller-Buschbaum¹ — ¹TU München, Physik - Department E13, James-Franck-Str. 1, D-85747 Garching, Germany — ²Uni. Potsdam, Inst. Chemie, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm, Germany — ³ILL, b.p. 156, 38042 Grenoble, France

Poly(N-isopropylacrylamide) (PNIPAM) is one of the prominent stimuli-sensitive hydrogels for the construction of nanoscale sensors which are sensitive to water and to water vapour (humidity). We choose PNIPAM end-capped with n-butyltrithiocarbonate (nbc-PNIPAM), a very short hydrophobic end group, to introduce an internal ordering and increase the mechanical stability in the films without sacrificing the swelling ability seriously. Two different gold layers with 0.4 nm and 5 nm thickness are coated on the nbc-PNIPAM surface by sputtering. The surface and internal structure of the dry films are characterized with AFM and GISAXS. The lower critical solution temperature (LCST) of the films in the water vapour is determined with white light interferometry. The temperature dependent swelling and switching kinetics in water vapour of such sensor films is probed by in-situ neutron reflectometry. The real time water diffusion and thickness changes for the two different gold layer thicknesses are compared and discussed in the framework of sensor applications. [1] W. Wang et al., Macromolecules 41, 3209-3218 (2008)