Incorporation of iron oxide nanoparticles into temperature-responsive poly (N-isopropylacrylamide-co-acrylic acid) P (NIPAAm-AA) polymer hydrogel

Magnetic polymer particles have attracted much attention because of their ubiquitous use in biomedical field such as biomolecule separation, drug carriers, imaging and etc. Iron oxide magnetic nanoparticles were incorporated into temperature responsive poly (N-isopropylacrylamide) (PNIPAAm) polymer hydrogel by a seed polymerization following a surface modification step. Iron oxide magnetic nanoparticles (50–100 nm) prepared by co-precipitation method were modified with silica (SiO₂) and 3-(trimethoxysilyl) propyl methacrylate (MPS) to introduce polymerizable vinyl group (−CH = CH₂) at the surface of the nanoparticles. Then, the Fe₃O₄/SiO₂/MPS particles were used as seed in polymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA). Here N, N’-methylenebisacrylamide (MBA) and potassium persulphate (KPS) were used as a cross-linker and initiator respectively. Dynamic Light scattering (DLS) results indicated a decrease of hydrodynamic diameter of magnetic Fe₃O₄/SiO₂/MPS/poly (NIPAAm-AA) polymer particles with increasing temperature. Surface functionality and polymer coating, morphology, chemical composition and presence of iron oxide in the magnetic polymer particles were evaluated by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) respectively. The content of magnetic part was more than 50 wt.% determined by TGA, satisfactory for separation of the final particles from a dispersed media by external magnet. Therefore, the magnetic polymer particles prepared here could be a potential candidate for separation technology.