Synthesis of Responsive Polymer Brushes on Magnetic Nanoparticles
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Synthesis of Responsive Polymer Brushes on Magnetic Nanoparticles Kamlesh J. Suthara, Joseph E. Mowata,c, Shankar Balasubramanianb, Muralidhar K. Ghantasalac, and Derrick C. Mancinia a
Advanced Photon Source, b Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL – 60439 c Department of Mechanical and Aeronautical Engineering, Western Michigan University, 1903, West Michigan Avenue, Kalamazoo, MI - 49008 ABSTRACT We report a simple synthesis technique to attached poly(N-isopropylacrylamide) on magnetic nanoparticles. Fe3O4 magnetic nanoparticles were prepared using co-precipitation method. Nearly monodisperse nanoparticles were separated by terminating surface of Fe3O4 with dopamine followed by careful centrifugation and decantation. NHS/EDC coupling chemistry was employed to attached the carboxylic acid terminated poly(N-isopropylacrylamide) to amine end of dopamine on surface of the magnetic particles. Analysis of the polymer brush layers was conducted using UV-Vis spectroscopy, ATR−FTIR, and Transmission electron microscopy techniques. The magnetic property was investigated using direct current superconducting quantum interference device (DC-SQUID) method. INTRODUCTION Nanocomposite structures consisting of magnetic nanoparticles decorated with thermoresponsive polymer are emerging as promising candidates for biomedical applications due to their size, biocompatibility, and magnetic properties. Temperature-sensitive polymers are often water-soluble and can be environmentally sensitive materials. They exhibit a volume-phase change behavior in response to changes in temperature through lower critical solution temperature (LCST). Magnetic nanoparticles, such as Fe3O4 and Fe2O3, are frequently used due to their high degree of magnetization. This combination of functionality, temperature-sensitivity from the polymer and magnetic field sensitivity from nanoparticles, is very promising for applications in from drug delivery [1, 2] and biological imaging using MRI [3, 4] to bulk materials as a bio-mimetic actuator [5, 6]. The phase change can be achieved either by increasing the temperature of the surrounding solution or by application of alternating magnetic field [7-9]. It is important to have individual particles homogeneously covered with polymer for their consistent and predictable behavior [9]. It is also important to protect the magnetic nanoparticles against oxidation and acid erosion. Moreover, producing a homogeneous ferrogel consisting of magnetic nanoparticles in a bulk hydrogel is a challenging task. One way to produce homogeneous ferrogels is to synthesize them with a monodispersed nanoparticle composite precursor. Thus, homogeneity can be achieved by better controlling the agglomeration characteristics compare to incorporating bare magnetic nanoparticles in hydrogel. This can improve the overall particle-distribution within the ferrogel and hence can contribute to better homogeneity of the ferrogel morphology and hence it’s the magnetic properties.
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