Aggregation of superparamagnetic iron oxide nanoparticles in dilute aqueous dispersions: Effect of coating by double-hydrophilic block polyelectrolyte
Abstract
tPolymer-coated superparamagnetic iron oxide nanoparticles (SPION) in aqueous dispersion wereprepared by the coassembly of SPION coated by an oleate bilayer with the double hydrophilic block poly-electrolyte poly[(3,5-bis(trimethylammoniummethyl)-4-hydroxystyrene iodide]-block-poly(ethyleneoxide) (QNPHOS-PEO) and characterized by TEM and AFM. It was found that the coating by QNPHOS-PEOaffects their aggregation into larger structures on the micrometer length scale observed by small-anglelight scattering as well as the dynamics of the dispersion observed by dynamic light scattering.
Oleate-SPION in aqueous dispersions form compact aggregates with the fractal dimension, D = 2.4, and thecharacteristic size about 2 μm which exhibit internal dynamics manifesting itself by the presence ofthe relaxation mode with τ ~ q(-3). In the case of QNPHOS-PEO/oleate-SPION dispersions, the polyelec-trolyte coating promotes the formation of compact clusters with the size of the order of ~10(2) nm.
The clusters, weakly interacting by magnetic dipolar interactions, form linear chainlike aggregates with thelow fractal dimension, D = 1.2. The dynamics of the QNPHOS-PEO/oleate-SPION dispersions observed byDLS is dominated by the diffusion of the clusters.