Soft ULC Microgels at the Interface Interact and Flow as Hertzian‐Like Colloids

Advanced Materials Interfaces, vol. 12

Abstract

Abstract Soft pair potentials predict a reentrant liquid phase for high concentrations, a behavior not observed experimentally. Here, very soft microgels confined at an oil‐water interface are used as a model system of particles interacting via a soft potential in 2D. Interfacial rheology measurements demonstrate the existence of different flow regimes that depend on the compression of the monolayer. Such a compression also leads to a non‐monotonic variation of the elastic moduli and of the yield stress of the monolayer. These results, together with the equilibrium phase behavior of the monolayer, are reproduced in molecular dynamics simulations of a 2D system of particles interacting with a Hertzian‐like potential. Remarkably, due to the non‐monotonic variation of the elastic moduli, we observe isoelastic points where the monolayer shows the same stiffness at very different concentrations. These points are the experimental manifestation of the predicted reentrant liquid phase.

Authors 6

1. José Ruiz‐Franco

   Universitat de Barcelona

   Affiliation as printed

   Department of Condensed Matter Physics University of Barcelona Barcelona 08028 Spain

   Institute of Complex Systems (UBICS) University of Barcelona Barcelona 08028 Spain

2. Tom Höfken Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

3. Maximilian M. Schmidt Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

4. Steffen Bochenek Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

5. Emanuela Zaccarelli corresponding

   Institute for Complex Systems · National Research Council · Sapienza University of Rome

   Affiliation as printed

   Department of Physics Sapienza University of Rome Piazzale Aldo Moro 2 Rome 00185 Italy

   Italian National Research Council ‐ Institute for Complex Systems (CNR‐ISC) Sapienza University of Rome Piazzale Aldo Moro 5 Rome 00185 Italy

6. Andrea Scotti corresponding

   Lund University

   Affiliation as printed

   Division of Physical Chemistry Lund University Lund SE‐22100 Sweden