Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: (Hydro)gels and Elastomers

CPP 20.1: Talk

Wednesday, March 28, 2012, 09:30–09:45, C 264

Kinetics of structural changes in thermoresponsive blockcopolymer solutions — Joseph Adelsberger¹, Ezz Metwalli¹, Alexander Diethert¹, Achille M. Bivigou-Koumba², André Laschewsky², Isabelle Grillo³, Peter Müller-Buschbaum¹, and •Christine M. Papadakis¹ — ¹TU München, Physikdepartment, Physik weicher Materie, Garching — ²Universität Potsdam, Institut für Chemie — ³Institut Laue-Langevin, Grenoble

Thermoresponsive polymers exhibit lower critical solution temperature (LCST) behavior and are of great interest for applications in ultrafiltration, in sensors or in transport/delivery systems.

We have studied triblock copolymers consisting of two hydrophobic polystyrene end blocks and a hydrophilic poly(N-isopropyl acrylamide) middle block. In aqueous solution, they form core-shell micelles or micellar networks [1]. The structural changes occurring after rapid heating above the cloud point were followed using time-resolved small-angle neutron scattering experiments [2]. Both, the polymer concentration and the target temperature were varied. The PNIPAM shell shrinks and releases water very rapidly. The collapsed micelles form small fractal aggregates, which become denser. Their growth first follows the diffusion-limited aggregation, whereas later, the clusters grow by coagulation. Depending on the target temperature, a skin effect is observed at the cluster surface.

[1] J. Adelsberger, C. M. Papadakis et al., Macromolecules 43, 2490 (2010). [2] J. Adelsberger, C.M. Papadakis et al., Macromol. Rapid Commun., accepted.