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

Abstract

Activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) of di(ethylene glycol) methyl ether methacrylate (M(EO)2MA) was successfully conducted in miniemulsion at 65 °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)2MA becomes hydrophobic above 25 °C. The polymerization was well-controlled with a mild water-soluble reducing agent, hydrazine, yielding PM(EO)2MA homopolymer with narrow molecular weight distribution (Mw/Mn = 1.2−1.6). Using this technique, well-defined PM(EO)2MA 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 a model for hydrophilic drugs. The drug releasing behavior can be well-controlled by both temperature and addition of reducing agent, indicating that the PM(EO)2MA magnetic microgels could find potential application for controlled targeted drug delivery.