Thermally Responsive PM(EO)2MA Magnetic Microgels via Activators Generated by Electron Transfer Atom Transfer Radical Polymerization in Miniemulsion

Activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) of di(ethylene glycol) methyl ether methacrylate (M(EO)(2)MA) was successfully conducted in miniemulsion at 65 degrees C. The reaction system was stable without diffusion of monomer and polymer into the aqueous phase because the monomer is water-insoluble and PM(EO)(2)MA becomes hydrophobic above 25 degrees C. The polymerization was well-controlled with a mild water-soluble reducing agent, hydrazine, yielding PM(EO)(2)MA homopolymer with narrow molecular weight distribution (M-w/M-n = 1.2-1.6). Using this technique, well-defined PM(EO)(2)MA microgels were prepared with degradable disulfide cross-linker. The microgels became magnetic after physically loading oleic acid-coated Fe3O4 nanoparticles, which could not diffuse out of the microgels due to their hydrophobicity. Thermally responsive and drug loading-releasing behavior of the magnetic microgels was studied using Rhodamine B as it model for hydrophilic drugs. The drug releasing behavior call be well-controlled by both temperature and addition of reducing agent, indicating that the PM(EO)(2)MA magnetic microgels could find potential application for controlled targeted drug delivery.