Synthesis of Thermosensitive Polymer-Magnetite Nanocomplexes via Atom Transfer Radical Polymerization

Researchers in Blacksburg, Virginia, have successfully synthesized polymer-magnetite nanoparticle complexes that respond to both magnetic fields and temperature. These novel complexes were created using alkyl halide-functional bis(diethylphosphonate) esters as initiators for polymerizing N-isopropylacrylamide via controlled atom transfer radical polymerization. The phosphonate esters were removed after polymerization, resulting in poly(N-isopropylacrylamide) with a bis(phosphonic acid) moiety precisely placed at one terminus. The bis(phosphonic acid) endgroups were then adsorbed onto magnetite nanoparticles, forming stable and colloidally-stable complexes in physiological media.

Key Takeaways:

• Researchers developed a method to synthesize polymer-magnetite nanoparticle complexes that respond to both magnetic fields and temperature using controlled atom transfer radical polymerization.
• Alkyl halide-functional bis(diethylphosphonate) esters were utilized as initiators for polymerizing N-isopropylacrylamide, and the resulting phosphonate esters were removed after polymerization.
• The bis(phosphonic acid) endgroups were adsorbed onto magnetite nanoparticles, yielding stable and colloidally-stable complexes in physiological media.
• The complexes exhibited thermosensitive aggregation behavior near the lower critical solution temperature of the poly(N-isopropylacrylamide) component.
• The researchers used a density distribution model to predict the hydrodynamic sizes of the complexes, which showed good agreement with measured sizes.
• The phosphonate esters provided a robust anchoring moiety onto the magnetite, allowing for stable complex formation.
• The complexes were primarily discrete, non-agglomerated nanoparticles.

Statistics:

• The lower critical solution temperature (LCST) of the poly(N-isopropylacrylamide) component was near 32°C.
• The hydrodynamic sizes of the complexes were predicted using a density distribution model and measured sizes of the magnetite cores.
• The complexes exhibited thermosensitive aggregation behavior, with a transition temperature near the LCST.

Sources:

• Pothayee, N., et al. "Synthesis of 'ready-to-adsorb' polymeric nanoshells for magnetic iron oxide nanoparticles via atom transfer radical polymerization." Polymer 52.6 (2011): 1356-1366.
• J.S. Riffle, Virginia Polytechnic Institute & State University, Macromolecular & Interfaces Institute, Blacksburg, VA 24061, United States.
• Elsevier Science Ltd., the Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, Oxon, England.