The design of well-defined PDMS–Magnetite complexes

Magnetic nanoparticles have numerous applications, particularly in biological systems for drug delivery, cell targeting, and as MRI contrast agents. This paper addresses the synthesis and characterization of well-defined magnetite nanoparticles coated with tricarboxylate-functional polydimethylsiloxane (PDMS) oligomers of varying molecular weight. Two methods – co-precipitation of iron chlorides and high-temperature reduction of iron(III) acetylacetonate – were used to synthesize the magnetite nanoparticles and compared. Through implementation of a polymer brush model, it was determined that the co-precipitation synthesis method required multiple magnetic separations and significant material loss to produce a well-defined particle distribution. Conversely, the high-temperature synthesis method showed a well-defined particle distribution without any magnetic separation. Through adjustment of critical design parameters such as polymer loading and molecular weight, the diameters of the complexes were predicted to within seven percent of experimental values. This demonstrates a tool for the design of sterically-stabilized single–particle complexes with a specifically tailored particle size.