Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 54: Poster Session 3

CPP 54.58: Poster

Donnerstag, 3. April 2014, 15:00–19:00, P2

Measurement of microviscosity in crosslinked polyacrylamide-ferrohydrogels by Mössbauer spectroscopy — •Joachim Landers¹, Lisa Roeder², Annette Schmidt², and Heiko Wende¹ — ¹Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg -Essen, Germany — ²Department Chemie, Institut für Physikalische Chemie, Universität zu Köln, Germany

Several polyacrylamide (PAAm) hydrogels with different amounts of methylenbisacrylamide (MBA) crosslinker were prepared, containing acicular hematite (α-Fe₂O₃) nanoparticles. These were used as probes allowing us to examine the local dynamic properties by ⁵⁷Fe-Mössbauer spectroscopy in systems with different degrees of cross-linkage. While static sextet spectra can be observed up to 265K, the width of the sextet lines increases dramatically near the water melting point in all samples, verifying movement of the nanoparticles when the hydrogel approaches the liquid state. This reveals that, contrary to expectations, embedded nanoparticles are not completely immobilized even in strong crosslinked hydrogel networks with us being able to quantify the effects of Brownian motion by Mössbauer spectroscopy. Theoretical calculations allow to estimate the temperature dependent microviscosity ν, which exceeds ν_H2O by far and is correlated to the amount of MBA crosslinker. (This work was supported by DFG WE2623/7-1, SPP1681)