Lamellar Diblock Copolymer Films with Embedded Maghemite Nanoparticles

Hybrid films composed of lamella forming polystyrene-d8-block-poly(n-butyl methacrylate) (PSd-b-PBMA) diblock copolymer (DBC) and PS-coated maghemite (gamma-Fe2O3) nanoparticles (NPs) are investigated. The structure of the hybrid films is systematically probed from the air-polymer interface to the substrate-polymer interface using time-of-flight grazing incidence small angle neutron scattering (TOF-GISANS). The affinity of the PS-coated NPs to the PSd nanodomains results in a well-controlled arrangement of the NPs within the parallel lamella DBC morphology, with a characteristic periodic distance expanding from 45 to 51 nm with progressive increase of NPs upload. In particular, the highly ordered parallel lamella morphology of the hybrid films is maintained at low NP concentrations. At high NP concentrations, the characteristic long-range ordered morphology is lost due to the strong affinity of neighboring NPs to aggregates, forming unguided large sized particle aggregates. The complementary results of real-space characterizations including profilometry, atomic force microscopy, and scanning electron microscopy are consistent with the observation obtained from TOF-GISANS. The potential applications in relation to medical instrumentation and magnetic sensors are highly feasible based on the superparamagnetic behaviors of the fabricated hybrid films, proven with a superconducting quantum interference device magnetometer.