Stabilization and controlled association of superparamagnetic nanoparticles using block copolymers

Abstract

International audienceMixing in aqueous solutions polyelectrolyte-neutral block copolymers with oppositely charged species, spontaneously forms stable core-shell complexes, which are electrostatically driven. We report here on the structural and orientational properties of such mixed magnetic nanoclusters made of magnetic iron oxide nanoparticles (MNP) and polyelectrolyte-neutral block copolymers. Small Angle Neutron Scattering and Transmission Electron Microscopy experiments allows to probe the innercore nanoparticle organization, leading to an average inter-particle distance and confirming the hierarchical internal structure of the clusters. Thanks to the MNP optical anisotropy, we also probe the under-magnetic field orientational properties of the core-shell clusters and their dynamical rotational relaxation

Two-stage kinetics of field-induced aggregation of medium-sized magnetic nanoparticles

“…To prevent their aggregation by magnetic interactions in zero field, they have to be superparamagnetic. So, these particles are usually porous nanoclusters composed of smaller 10-nm superparamagnetic nanoparticles [52][53][54][55][56] . Similarly to small nanoparticles, medium-sized colloids exhibit condensation phase transitions 54,55,57 which enhance drastically their magnetic separation on magnetized collectors [57][58][59][60][61] .…”

Polydimethylsiloxane (PDMS) Coating onto Magnetic Nanoparticles Induced by Attractive Electrostatic Interaction

“…First, polyacrylic acid polymer (2,100 g/mol, noted PAA2k) is selected to stabilize iron oxide nanoparticles in water [22,23] at pH from 4 to 11. We already demonstrated that this coating provides both stability and post functionalization to prepare controlled aggregates, either spherical [24] or elongated [25,26]. In a second step, aminopropylmethylsiloxane-co-dimethylsiloxane block copolymer (PDMS-co-APMS) is used to add a hydrophobic coating to the NPPAA (Figure 1).…”

Aggregation of superparamagnetic iron oxide nanoparticles in dilute aqueous dispersions: Effect of coating by double-hydrophilic block polyelectrolyte

“…Double hydrophilic block polyelectrolytes (DHBP), that is, block copolymers consisting of a hydrophilic neutral block and a polyelectrolyte block, represent a promising group of materials that can be used for stabilizing magnetic SPION in aqueous dispersions [14,16,17]. The DHBP layer can simply be formed by mixing electrostatically stabilized coated SPION with an oppositely charged DHBP.…”

“…The DHBP layer can simply be formed by mixing electrostatically stabilized coated SPION with an oppositely charged DHBP. Electrostatic co-assembly of both components leads to the formation of mixed nanoparticles with protective shells formed by the neutral block of the DHBP which are stable in diluted dispersion, even though the selfassembly process usually leads to the formation of small SPION clusters that form the core of the hybrid co-assembled particle [17]. Coating by DHBP represents a generally applicable process leading to the formation of biocompatible colloids with many potential applications.…”