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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 41: Charged Soft Matter, Polyelectrolytes and Ionic Liquids I
CPP 41.2: Talk
Friday, March 21, 2025, 10:00–10:15, H38
Surface Charged Polymeric Micelles - A Tunable Model System Studied by SANS — Lingsam Tea1, Luis Willner1, Christin Waldorf1, Olga Matsarskaia2, Ralf Schweins2, Stephan Förster1, Lutz Willner1, and •Jörg Stellbrink1 — 1JCNS-1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany — 2Institut Laue-Langevin, 38042 CEDEX 9 Grenoble, France
We investigate surface charged micelles in aqueous solution formed by carboxy terminated n-octacosyl-poly(ethylene oxide) block copolymers, C-PEO5-COOH with 5 the PEO molar mass in kg/mol, by small angle neutron scattering (SANS), zeta-potential measurements and rheology. The -COOH end group was introduced by selective oxidation of the CH3OH end group of a C-PEO5-OH precursor using Bobbitt’s salt. Micellar solutions of different concentrations in the dilute and semidilute range were investigated at pH 2, 6 and 12 to vary ionic strength and the number of effective surface charges Z. Z was further varied by using mixtures of C-PEO5-COOH and C-PEO5-OH at different mixing ratios. SANS measurements reveal that the intramicellar form factor is identical at the different pH-values which implies that the individual micellar structure is unaffected by the number of surface charges. On the contrary, the intermicellar structure factor and the phase behavior show a strong dependence on Z. In particular, we observe a distinct shift of the liquid - fcc crystal phase boundary. A quantitative analysis in terms of a screened Hard Sphere Yukawa potential reveals a very good agreement between experiment and theory.
Macromolecules 2024, 57, 5818-5830
Keywords: Small Angle Neutron Scattering; Block Copolymer Micelles; Phase Diagram; Zeta Potential; Rheology