. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM184 NANOCOMPOSITE FERROGEL BEHAVIOUR UNDER AN APPLIED MAGNETIC FIELD: A SINGLE MOLECULE DIFFUSION STUDY  Ateyyah AL-Baradi*, Shaomin Mai**, Oleksandr Mykhaylyk**, Richard A. L. Jones*, and Mark Geoghegan* * Department of Physics and Astronomy, The University of Sheffield ** Department of Chemistry, The University of Sheffield . We study the physical properties of nanocomposite poly(methacrylic acid) (PMAA) ferrogels infiltrated with Fe3O4 in response to applied magnetic fields. Ferrogels provide an interesting form of control of polymer conformation when subject to magnetic fields. We have used fluorescence correlation spectroscopy (FCS) to measure the diffusion of single FITC-labelled dextran molecules within these PMAA/Fe3O4 nanocomposites and see that the diffusion coefficient of the dextran varies significantly as a function of magnetic field strength. We also determined the magnetically controlled molecular release from ferrogels to the surrounding solvent. Increasing the magnetic field induction from 0.2 T to 0.8 T reduces the quantity of dextran released by almost a factor of 2 at the highest concentration used (1 wt.%). Small-angle X-ray scattering (SAXS) was used to determine the size distribution of the magnetic nanoparticles in the gel medium. Scattering from these systems follows Porod’s law of scattering from smooth surfaces resulting in an average particle size of between 8 and 12 nm depending on the concentration of nanoparticles in feed. A swelling-collapse transition is observed as a function of magnetic field induction and nanoparticle concentration. By correlating the diffusion coefficient from the FCS measurements to a length scale associated with the pore size within the hydrogels revealed similar nanoparticle size distributions to those seen by SAXS. . © nanoAC . . . . . . . . . .

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