Regensburg 2025 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Nanostructures, Nanostructuring and Nanosized Soft Matter I

CPP 26.5: Vortrag

Mittwoch, 19. März 2025, 12:45–13:00, H34

In-situ investigation of the lateral and vertical structure of PNIPAM-microgels at the air-liquid and solid-liquid interfaces — Olaf Soltwedel, Joanne Zimmer, •Hayden Robertson, and Regine von Klitzing — Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, D-64289 Darmstadt, Germany

The novel surface characterisation approaches presented here highlight, for the first time, the use of both specular and off-specular X-ray reflectivity (XRR) to probe the vertical and lateral structure of adsorbed polymer microgels particles at various interfaces, offering in situ, non-invasive insights without the need for doping or transfer-induced artefacts. In particular, we demonstrate the complementarity of two readily accessible laboratory techniques on characterising the structure of adsorbed microgels: atomic force microscopy (AFM) and XRR. Initial ex situ AFM scans of Langmuir-Blodgett deposited microgels at the solid interface revealed strong lateral 2D hexagonal ordering across a broad range of surface pressures. However, for the first time, these results are confirmed by off-specular XRR, demonstrating the existence of the hexagonal long-range ordering at low and intermediate surface pressures for in situ conditions at the air-water interface. Upon uniaxial compression of the interface, the microgel lattice constants decrease monotonically, indicating tighter packing. At these higher surface pressures, both AFM and off-specular XRR also reveal the formation of microgel domains; hexagonal short-range ordering is maintained whereas long-range ordering is diminished.

Keywords: microgel; scattering; off-specular; AFM; lateral structure