Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Focus: Structure and Dynamics of Responsive Hydrogels I

CPP 3.8: Invited Talk

Monday, March 22, 2010, 12:15–12:45, H37

Dynamics of thermosensitive microgel particles — •Matthias Ballauff — Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin

We present a survey on recent studies on the dynamics of thermosensitive microgels in aqueous solution. The particles consist of a sold polystyrene core onto which a shell of corsslinked poly(N-isopropylacrylamide) (PNIPA) is grafted. As cores we use spherical particles as well as dumbbell-shaped colloids consisting of two spheres attached to each other. Depolarized dynamic light scattering (DDLS) gives quantitative information about the translational and rotational diffusion coefficient (1). The volume fraction of these particles can be adjusted by the temperature of the system in a continuous fashion. This allows us to study the rheology of such suspension up to high volume fractions. The moduli G' and G'' in the linear viscoelastic regime as well as the flow curves as the function of the shear rate are found to be in good agreement with the predictions of mode-coupling theory (2).

1. S. Bolisetty, M. Hoffmann, S. Lekkala, Th. Hellweg, M. Ballauff, L. Harnau, Coupling of Rotation Motion with Shape Fluctuations of Core-Shell Microgels Having Tunable Softness, Macromolecules 2009, 42, 1264-1269

2. M. Siebenbürger, M. Fuchs, H. H. Winter, M. Ballauff, Viscoelasticity and shear flow of concentrated, noncrystallizing colloidal suspensions: Comparison with mode-coupling theory, J. Rheol. 2009, 53, 707-726