Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Focus Session: Soft Matter and Nanocomposites: New Opportunities with Advanced Neutron Sources 2

CPP 44.5: Hauptvortrag

Freitag, 9. September 2022, 10:45–11:15, H38

Magnetic particle self-assembly at functionalized interfaces — •Max Wolff — Department for Physics and Astronomy, Uppsala University, Uppsala, Sweden

Neutrons allow the study of buried interfaces and are directly sensitive to magnetic induction. This makes grazing incidence neutron scattering an ideal tool for the study of self-assembled magnetic particles.

In this talk I will discuss the self-assembly of monodisperse colloidal magnetite nanoparticles from a dilute water-based ferrofluid onto functionalized silicon surfaces. The density of the layer adjacent to the substrate is determined by the interaction between the particles and the substrate. Dense layers form for chemical binding and magnetic substrates, while less dense and no layering is found for physisorption and repulsive interactions. Once adsorbed subsequent layers assemble due to magnetic dipolar forces. The layering gets more pronounced for larger dipole moments of the particles. Once formed the density and structure of the layers may be tuned by magnetic and/or shear fields.

Magnetic particles may also be used to self-assemble polymer micelles. Applied magnetic fields may result in a micro shear effect aligning the domains of micellar crystals. By stroboscopic reintegration this reorientation process may be followed on time scales down to ms and resonant enhancement may aid the identification of off-specular and grazing incidence small angle scattering.