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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: POSTER: Micro and Nano Fluidics

CPP 19.8: Poster

Mittwoch, 28. März 2007, 16:00–18:30, Poster B

Rheological and structural phase diagrams of salted solutions of the tri-block copolymer EO₂₀-PO₇₀-EO₂₀ — •Nicole Voss¹, Marco Walz¹, Max Wolff², and Andreas Magerl¹ — ¹Chair for Crystallography and Structural Physics, University of Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen — ²Chair for Condensed Matter Physics, Ruhr-University Bochum, Universitätsstr. 150, 44780 Bochum

Aquaeous solutions of tri-block copolymers have well known rich phase diagrams of ordered structures which can also be identified through rheometry. We have studied the influence of adding electron-rich salts with concentrations up to 1.5 mol/dm³ on the phase diagram of the tri-block copolymer Pluronic^.07exR20D P123 (central block of 70 propylene oxide units terminated by two end groups of 20 ethylene oxide units). While the morphology of the phase diagram is preserved, a linear shift of -12^∘C per 1 mol/dm³ CsCl is observed for the phase boundary of the cubic phase with high viscosity. The results are interpreted by the modification of the water structure, i. e. the ions of CsCl surround themselves with hydration shells and also dehydrate the PPO block. This mechanism decreases the solubility of the polymer and favours micellization at lower temperatures.
The authors gratefully acknowledge financial support by the DFG grants MA801/12-1 and ZA161/18-1 within the priority program (SPP) 1164.