Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 4: Focus: Structure and Dynamics of Responsive Hydrogels II
CPP 4.4: Vortrag
Montag, 22. März 2010, 15:00–15:15, H37
Free volume and swelling in thin films of poly(N-isopropylacrylamide) end-capped with n-butyltrithiocarbonate — •Stephan Harms1, Klaus Rätzke1, Franz Faupel1, Werner Egger2, Luca Ravelli2, André Laschewsky3, Weinan Wang4, and Peter Müller-Buschbaum4 — 1CAU Kiel, Institut für Materialwissenschaft - Materialverbunde — 2Universität der Bundeswehr München — 3Potsdam Universität, Inst. Chemie — 4TU München, Physik-Department LS E13
Thin hydrogel films of poly(N-isopropylacrylamid) end-capped with n-butyltriocarbonate (nbc-PNIPAM) show a thickness dependent swelling behavior, i.e. the thinner the films, the more they can swell, normalized to the respective thickness [1]. A tentative explanation is centered on differences in free volume. As the o-Ps lifetime is a generally accepted measure for the average free volume, positron annihilation lifetime spectroscopy as function of energy is performed to obtain depth profiles of the free volume of nbc-PNIPAM films with thicknesses from 40 to 200 nm. The results clearly show higher o-Ps lifetimes and hence higher free volume for thinner films. Results are discussed with respect to free volume and mobility influences on sorption and swelling behavior.
[1] Wang W., Troll K., Kaune G., Metwalli E., Ruderer M., Skrabania K., Laschewsky A., Roth S.V., Papadakis C.M., Müller-Buschbaum P.; Macromolecules 2008, 41, 3209