SKM 2023 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 35: Poster Session II
CPP 35.61: Poster
Wednesday, March 29, 2023, 11:00–13:00, P1
Effect of pressure on the micellar structure of PMMA-b-PNIPAM in aqueous solution — •Pablo A. Alvarez Herrera1, Geethu P. Meledam1, Cristiane Henschel2, Leonardo Chiappisi3, André Laschewsky2, and Christine M. Papadakis1 — 1TU München, School of Natural Sciences, Garching Germany — 2Universität Potsdam, Institut für Chemie, Potsdam-Golm, Germany — 3Institut Laue- Langevin, Grenoble, France
In aqueous solution, amphiphilic diblock copolymers consisting of a permanently hydrophobic and a thermo-responsive block self-assemble into core-shell micelles. In particular, poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) (PMMA-b-PNIPAM) forms micelles featuring a hydrophobic PMMA core and a thermo-responsive PNIPAM shell. This phase transition can be also induced by changing the pressure. Here, we study the effect of pressure on the micellar structure of PMMA-b-PNIPAM in aqueous solution by small-angle neutron scattering (SANS). In temperature-resolved experiments, we find that the micellar shell strongly dehydrates after crossing the co-existence line at 0.1 MPa. At 75 MPa, on the contrary, it remains hydrated and the micelles are highly-correlated within the aggregates. We also characterized the micellar structure in a pressure-resolved experiment at 31.8 ∘C. In this case, we find that, after crossing the co-existence line, the micellar shell appreciably shrinks, even though it remains partially hydrated. We conclude that the micellar structure in the two-phase region strongly depends on pressure.