Printed Thin Magnetic Films via Ternary Hybrid Diblock Copolymer Films Containing Magnetic Iron Oxide and Nickel Nanoparticles

Ternary hybrid thin films composed of a diblock copolymer templating two types of nanoparticles (NPs) expand the functionality of binary systems, which renders them interesting for magnetic sensing or magnetic data storage applications. Herein, one-pot slot-die printed hybrid polystyrene-<i>block</i>-poly(methyl methacrylate) (PS-<i>b</i>-PMMA) thin films are prepared with iron oxide (magnetite, Fe₃O₄, <i>d</i> = 20 nm) and nickel NPs (Ni, <i>d</i> = 46 nm) in one step by the advanced slot-die coating technique, which facilitates upscaling of fabrication. The evolution of the hybrid film morphology is probed with in situ grazing-incidence small-angle X-ray scattering and compared to that of a PS-<i>b</i>-PMMA thin film without NPs. Additionally, scanning electron microscopy and atomic force microscopy are used to analyze the surface morphology of hybrid films with an increasing NP content after deposition. It is found that different from the pure PS-<i>b</i>-PMMA thin film drying kinetics with five stages, the ternary hybrid film formation can be divided into four stages that are attributed first to the wet film, solvent evaporation, a subsequent rapid coalescence and microphase separation, and finally the dry film. The magnetic properties of the hybrid thin films are investigated with a superconducting quantum interference device magnetometer. All hybrid films are ferrimagnetic and with increasing nickel weight percent in the hybrid film, while the iron oxide weight percent is kept constant, the magnetic properties of the film are modulated accordingly.