pH Responsive Behavior of Fe₃O₄@PDEA-PEGMA Core-Shell Hybrid Magnetic Nanoparticles

Fe3O4@PDEA-PEGMA core-shell magnetic nanoparticles were prepared via surface-initiated atom transfer radical polymerization (ATRP). First, an ATRP initiator was immobilized onto the surface of Fe3O4 magnetic nanoparticles, then poly[2-(diethylamino)ethyl methacrylate] (PDEA) and poly(poly[(ethylene glycol) monomethacrylate]) (PEGMA) were grafted from the surface of the magnetic nanoparticles in succession. Each step of the reactions gave distinctive thermogravimetric analysis curves. Polymer shells cleaved from Fe3O4 core were measured by gel permeation chromatography, while its molecular weight was found to increase with successive polymerization (with a polydispersity of approximately 1.3–1.4). The architecture of the core-shell nanoparticles was confirmed by transmission electron microscopy. The Fe3O4@PDEA-PEGMA hybrid magnetic nanoparticles formed stable dispersions in H2O at low pH (pH < 6) and precipitated out at high pH (pH > 6). This pH transition behavior was also observed in dynamic light scattering experiments.