Polymer nanocomposites have been intensively investigated because they exhibit both the properties of the polymers and the properties of the nanoparticles. Of particular importance are superparamagnetic iron oxide polymer nanocomposites. Their properties can be modified by application of an external magnetic field.[1-4] It has been shown, that the properties of superparamagnetic nanocomposite materials depend strongly on the distribution of the nanoparticles in the nanocomposite and on cluster formation. A method to protect those nanoparticles from clustering during the preparation of polymer nanocomposites is the encapsulation of the nanoparticles. We encapsulated monodisperse superparamagnetic iron oxide nanoparticles (SPIONs) with an amphiphilic diblock copolymer. For this purpose, we used a polymer with carbon-carbon double bonds which we crosslinked in a thiol-ene clickreaction to stabilize the polymer shell surrounding the particles. We dispersed those stabilized nanoparticles into a polymeric matrix and characterized the nanocomposites with small angle x-ray scattering (SAXS). Those investigations demonstrated the presence of mostly single particles and a negligible amount of dyads. By applying an external magnetic field during SAXS measurements we obtained anisotropic scattering images due to an agglomeration of the particles induced by magnetic interactions between the SPIONs. By removal of the external magnetic field, the agglomerates are dispersed, leading to an isotropic scattering image with again mostly single particles.
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5. A. Feld, R. Koll et al., ACS Nano 2017, 11, 3767-3775.