Self-assembly of diblock copolymer-maghemite nanoparticle hybrid thin films

The arrangement of maghemite (γ-Fe₂O₃) nanoparticles (NPs) in poly(styrene-d8-block-n-butyl methacrylate) P(Sd-b-BMA) diblock copolymer (DBC) films via a self-assembly process was investigated toward the fabrication of highly ordered maghemite-polymer hybrid thin films. The resulting thin films exhibited a perforated lamella with an enrichment layer containing NPs as investigated with X-ray reflectometry, scanning electron microscopy, atomic force microscopy, and time-of-flight grazing incidence small angle neutron scattering as a function of the NP concentrations. The NPs were selectively deposited in the PSd domains of the DBC during the microphase separation process. At low NP concentrations, the incorporation of the NPs within the DBC thin films resulted in an enhanced microphase separation process and formation of highly oriented and ordered nanostructured hybrid films. At higher NP concentrations, the aggregation of the NPs was dominating and large sized metal oxide clusters were observed. The superparamagnetic properties of the metal oxide-polymer hybrid films at various NP concentrations were probed by a superconducting quantum interference device magnetometer, which shows that the hybrid films are highly attractive for optical devices, magnetic sensors, and magnetic recording devices.