Regensburg 2025 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Gels, Polymers Networks and Elastomers I

CPP 1.4: Vortrag

Montag, 17. März 2025, 10:30–10:45, H34

Aqueous foams stabilized by PNIPAM microgels: A multi-scale investigation — •Joanne Zimmer, Luca Mirau, Gaëtan Barth, and Regine von Klitzing — Soft Matter at Interfaces, Institute for Condensed Matter Physics, TU Darmstadt, Hochschulstraße 8, D-64289 Darmstadt

Foams possess several structural motifs on different length scales with the smallest building blocks being the foam films or even the liquid/air interface. In this work, PNIPAM microgels (MG) are used as foam stabilizers as they are highly interfacial active and temperature responsive. In addition, the MG stiffness and by this their interfacial activity can be tuned by variation of the crosslinker content. We present a multi-scale approach towards understanding how the MG properties are related to the macroscopic foam and foam film stability. Spatially resolved disjoining pressure isotherms are measured with a Thin Film Pressure Balance (TFPB). The isotherms provide information about the film thickness, surface mobility and film stability. These properties are correlated with macroscopic foam characteristics such as foamability, stability and drainage dynamics. Indeed, the results are in good agreement on all length scales: A lower crosslinker content supports foam formation due to a faster surface coverage and results in an increased foam stability, as a more rigid surface layer is formed. Increasing the amount of crosslinker in the MG induces a transition from Poiseuille flow to plug flow in the foam during drainage which coincides with an increasing mobility of the surface of a single foam film measured in a TFPB.

Keywords: Aqueous foams; Foam films; liquid/air interface; PNIPAM microgels