Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Poster Session I

CPP 20.13: Poster

Monday, March 12, 2018, 17:30–19:30, Poster A

SANS Study on the Pressure-Dependence of the Cononsolvency Effect in Aqueous PNIPAM Solutions — •Bart-Jan Niebuur¹, Kora-Lee Claude¹, Ralf Schweins², Vitaliy Pipich³, Marie-Sousai Appavou³, Alfons Schulte⁴, and Christine M. Papadakis¹ — ¹TU München, Physik-Department, Garching, Germany — ²Institut Laue-Langevin, Grenoble, France — ³JCNS at MLZ, FZ Jülich, Garching, Germany — ⁴University of Central Florida, Department of Physics, Orlando, U.S.A.

The solubility of the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM) in aqueous solutions decreases drastically when small amounts of methanol are added, resulting in a reduced cloud point, an effect called cononsolvency. If high pressure is applied, the cononsolvency effect is destroyed, meaning that the cloud point is clearly higher in comparison with PNIPAM solutions in pure water at the same pressure. Using small-angle neutron scattering, the phase behavior of semi-dilute PNIPAM solutions in mixtures of water and methanol is studied in temperature scans at various pressures, revealing the behavior of the concentration fluctuations near the respective cloud points. The results show that high pressure strongly broadens the phase transition, revealing changes in the polymer-solvent interaction. Very small-angle neutron scattering allowed us to study the effect of methanol on the mesoglobule formation and the size of the mesoglobules in the segregated state of PNIPAM at high pressure.