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Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Poster 1

CPP 12.81: Poster

Monday, September 5, 2022, 18:00–20:00, P1

Free Expansion Melting of Colloidal Crystals based on Polystyrene Beads — •Marcus Witt, Josefine von Puttkamer-Luerssen, Ebrahim Malek, Jorge Meyerelles Jr., Max Hofmann, Johannes Wagner, Sabrina Juretzka, and Thomas Palberg — Johannes Guttenberg Universität Mainz, Institut für Physik, Staudingerweg 7, 55128 Mainz, Deutschland

The study reports the first realization of a three dimensional free-expansion melting. Imagine a polycrystalline metal sphere in micro-gravity and turning off the mutual attraction to observe the expansion and melting of the sphere. This gedankenexperiment can be mimicked with a suspension of charged colloidal spheres in deionized (DI) water. For 100nm spheres with several hundred charges the freezing density is at about 2*m−3. The corresponding lattice constant is of a few hundred nm and results in a brilliant Bragg scattering at visible wavelength. Diluting the colloidal crystal in DI water, the crystal melts and expand due to their mutual electrostatic repulsion. The expansion is monitored by RGB video microscopy with a illumination with white light (T=5000K). The scattered wavelength is analyzed under 90 to obtain the evolution and spatial distribution of the lattice constant. The polycrystalline drops expand in a concentric fashion, while individual crystals drift towards the (ideally spherical) melting zone.

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