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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Interfaces and Thin Films II

CPP 38.2: Vortrag

Donnerstag, 20. März 2025, 16:45–17:00, H38

PNIPAM Microgel-Stabilized Foam Films: Effect of Crosslinker Content and Purification State — •Luca Mirau, Joanne Zimmer, Kevin Gräff, Matthias Kühnhammer, and Regine von Klitzing — Institute for Condensed Matter Physics, TU Darmstadt, Germany

Aqueous foams find widespread application in fields such as cosmetics, food industry, oil recovery and fire-fighting. Their stabilization requires the presence of surface-active molecules or colloidal particles. In this study, thermoresponsive microgels (MGs) composed of poly(N-isopropylacrylamide) (PNIPAM) with varying crosslinker contents are applied as foam stabilizers, resulting in temperature-sensitive foams. Foam films serve as the fundamental building blocks of foams. The structuring of MGs within these films is analyzed using the Thin Film Pressure Balance (TFPB) technique. Foam films are formed within a pressure chamber, and their thickness is determined through interferometric methods under a light microscope. The foam films display an inhomogeneous structure comprising significant pattern formation, i.e. a network-like, several 100nm thick region containing MGs, interspersed with thin MG-depleted zones less than 100nm thick. The findings indicate that the crosslinking content plays a crucial role in MG layering within these thick network regions, influencing the film thickness. Additionally, the purification state of the MGs, monitored through interfacial tension measurements, governs the formation of thin zones in the foam films, which strongly affects their stability.

Keywords: Microgels; Thin Film Pressure Balance; Foams; Foam Films