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Surface Modification of Iron Oxide (Fe3O4) Micro- and Nano-particles with Stimuli Responsive Polymers

E.S. Vasquez, W.B. Nicholson, K.B. Walters
Mississippi State University, US

Keywords: ATRP, magnetic nanoparticles, thermo-responsive, pH-responsive


In this work, the synthesis of stimuli responsive polymer brushes was carried out using surface-initiated atom transfer radical polymerization (ATRP) on iron oxide (Fe3O4) micro- and nano-particles. Bare Fe3O4 nanoparticles (20 nm nom. d(H)) were first modified using a thiol SAM. After SAM addition, a bromine-based initiator was attached. Commercially available SAM-modified Fe3O4 micro- and nano-particles (1 micron and 200 nm nom. d(H)) were also obtained and bromine-based initiator was attached on the particle surface. After addition of the initiator, either poly(methacrylic acid) (PMAA), poly(N-isopropylacrylamide) (PNIPAM), or PMAA-b-PNIPAM was grown from the surface of the micro- and nano-particles. DRIFTS results confirmed the presence of PMAA as CH2 peaks at 2900-3000 cm-1 and a broad O-H stretch (3300 cm-1) are observed as the ATRP reaction was carried out. TEM measurements demonstrated nanomaterials with the magnetic nanoparticle core surrounded by amorphous material. One of the main goals of this study was to demonstrate the thermal response of the surface modified Fe3O4 nanoparticles. For this purpose, DLS measurements on 200 nm Fe3O4 grafted with PMAA-b-PNIPAM revealed decreased radius of gyration of the nanoparticles as temperature is increased. Therefore, DLS results demonstrate the thermo-responsive size change of these metal-polymer composite nanoparticles.
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