Abstract
Nanostructured diblock copolymer films with embedded magneticnanoparticles are prepared by solution casting. The diblock copolymerpolystyrene-block-polymethylmethacrylate with a fully deuterated polystyrene block of aweight ratio of 0.22 is used as a structure-directing matrix. Maghemite nanoparticles (γ-Fe2O3) are coated with polystyrene and thus have a selective affinity to the minority block of thediblock copolymer. The hybrid film morphology is investigated as a function ofnanoparticle concentration. The surface structure is probed with atomic force microscopyand scanning electron microscopy. The inner film structure and the structure atthe polymer–substrate interface are detected with grazing incidence small angleneutron scattering (GISANS). Irrespective of the nanoparticle concentration a welldeveloped micro-phase separation structure is present. From the Bragg peaksobserved in the GISANS data a linear nanoparticle concentration dependence of theinter-domain spacing of the micro-phase separation structure is determined. Thesuperparamagnetic and blocking behavior can be explained with a generalizedStoner–Wohlfarth–Néel theory which includes either an elastic torque being exerted onthe nanoparticles by the field or a broad distribution of anisotropy constants.
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