Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 35: Microfluidics II: Boundary conditions
CPP 35.5: Vortrag
Donnerstag, 26. März 2009, 15:15–15:30, ZEU 160
Shear induced relaxation of polymer micelles at the solid-liquid interface — •Max Wolff1, 2, 3, Roland Steitz4, Philipp Gutfreund1, 2, Nicole Voss5, Stefan Gerth5, Marco Walz5, Andreas Magerl5, and Hartmut Zabel1 — 1Institute for Solid State Physics/EP IV, Ruhr-University Bochum, Germany. — 2Insitute Laue-Langevin, Grenoble, France. — 3Materials Physics, Uppsala University, Sweden. — 4Helmholtz Centre Berlin for Materials and Energy, Berlin, Germany. — 5Crystallography and Structural Physics, University of Erlangen-Nürnberg, Erlangen, Germany.
Mixtures of amphiphilic block copolymers with a selective solvent are known to form various structures. Applying external fields such as shear can dramatically change the overall structure of the sample. In most cases, crystallites become aligned.
A 20 % aqueous solution of F127 was investigated by combining rheology in a cone/plate-geometry and surface-sensitive grazing incident neutron scattering. The crystalline structure formed by the polymer micelles becomes less pronounced for low shear rates, but correlations increase for higher shear rates. After stopping shear a slow relaxation of the micelles is found in the vicinity of a hydrophilic silicon wall, while a fast relaxation is observed in the boundary layer against the hydrophobic silicon wall (weak micelle-wall interaction). The results show that in the vicinity of the interface wall-particle interactions compete heavily with the shear force acting on the liquid [1].
[1] M. Wolff et al., Langmuir (Letter) 24, 11331 (2008).