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MM: Fachverband Metall- und Materialphysik

MM 29: Liquid and Amorphous Materials

MM 29.1: Vortrag

Donnerstag, 20. März 2025, 12:00–12:15, H10

Molecular Feuds and Fragment Tales: Exploring Cyanobiphenyl Liquid Crystals with Cryo Atom Probe Tomography — •Kuan Meng, Kang'an Wang, Sebastian Eich, and Guido Schmitz — Stuttgart University,Institute for Materials Science, Heisenbergstr. 3, 70569, Stuttgart, Germany

Liquid crystals exhibit the fascinating duality of liquid-like fluidity and solid-like long-range order, requiring nanoscale characterization techniques with high spatial resolution and chemical sensitivity. Atom probe tomography (APT) uniquely meets these requirements, offering unprecedented insights into the behavior of anisotropic organic molecules. This talk bridges liquid crystal science and APT by exploring cyanobiphenyl systems (5CB, 8CB, and 8OCB).

We investigated the field evaporation behaviors of these molecules, observing remarkable stability under high electric fields. Molecular signals dominated (90% for 5CB and 8CB, 70% for 8OCB), with fragmentation patterns influenced by oxygen atoms. The fragments were classified as alkyl chains, single phenyl derivatives, cyanobiphenyl residues, and cyano-hydrogen substitution pairs. Spatially, both molecular and fragment signals correlate strongly with laser orientation: fragmentation decreases from illuminated to shadowed regions, reflecting cleavage behavior under thermal gradient-induced field variations. Additionally, APT revealed the uniform mixing of 5CB and 8CB across various ratios, as well as the lattice plane of the crystal structure of pure 8CB. In the crystalline regions, we will discuss how the molecules field evaporate at specific angles relative to their intrinsic orientations.

Keywords: Cryo Atom Probe Tomography; Cyanobiphenyl; Liquid Crystal; Organic Molecules Field Fragmentation; Crystallography