Magnetic Nanoparticles in Polymer Films
Nanocomposite materials based on a polymer matrix and inorganic nanoparticles fillers are of great importance in research because the desired physical properties can be rendered to the final product. Target properties are largely dependent on the arrangement of nanoparticles in the host matrix used. For special application purpose an ordered arrangement of the nanoparticles is desired. An ordered arrangement of nanoparticles can be achieved by using the template offered by self organization of block copolymers. The idea is to incorporate nanoparticles into spherical, lamellar or cylindrical microdomains formed by micro-phase separation of the block copolymer, which can be done for example, either by removing one block and using as a mask for plating or by etching through the film and transferring the pattern to a solid substrate. Another method is to tailor the surface of nanoparticles in a way that the block copolymer self-assembles with the nanoparticles that organize themselves selectively in one block.
Coupling a self-assembly processes with a spatial arrangement of nanoparticles due to preferential interaction is a promising technique to establish ordered structures of the nanoparticles and its clusters. The nanostructures which are present in the films due to microphase separation and spatial arrangement of nanoparticles are investigated by the real-space techniques atomic force microscopy and scanning electron microscopy and by the reciprocal-space technique grazing incidence small-angle X-ray scattering (GISAXS).
The reported hybrid nanostructures are produced by spin coating without any further processing which marks a significant difference as compared to other published work due to its simplicity.
Depending on the ratio of nanoparticle diameter and characteristic spacing of the polymer matix on the one hand and film thickness and characteristic spacing on the other hand many different scenarios arise. In addition to simple incorporation surface assisted structures can be obtained: This new type of nanostructures comprising of maghemite nanoparticles masked by PS chains sitting on top of polymer superstructures is investigated. Due to the special selected spatial sizes of nanoparticles, lamellar thickness of diblock copolymer in bulk and film thickness, this new type of nanocomposite is formed. The particles are too big in size to allow for incorporation inside a diblock copolymer lamellae of the polymer matrix. The film thickness is too small to allow for establishing homogeneous films consisting of lamellae which are oriented parallel to the substrate. Moreover, the film thickness is that small, that dewetting is observed on the sample surface. Presence of PS chains on iron oxide core causes entanglement with polymer chains and thus prevents migration to substrate and results an arrangement of nanoparticles on top of polymer superstructures.
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Nanoparticles in diblock copolymer films investigated by off-specular neutron scattering;
Langmuir 19, 7783 (2003)
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Parallel and perpendicular lamellar phases in copolymer-nanoparticle multilayer structures;
Physica B 350, e939 (2004)
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Maghemite nanoparticles on supported diblock copolymer nanostructures;
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Correlated Roughness in Polymer Films Containing Maghemite Nanoparticles;
Macromolecules 41, 2186-2194 (2008) link
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Array of magnetic nanoparticles via particle co-operated self-assembly in block copolymer thin film;
Macromolecules 42, 6202-6208 (2009) link
Last change: June 5, 2012