Preparation and characterization of thermosensitive organic–inorganic hybrid microgels with functional Fe3O4 nanoparticles as crosslinker

Abstract A methodology is described for the preparation of thermosensitive organic–inorganic hybrid microgels with functional Fe 3 O 4 nanoparticles as the crosslinker and N -isopropylacrylamide (NIPAm) as the monomer. Magnetic Fe 3 O 4 nanoparticles were first prepared via a redox reaction in aqueous solution and then modified with 3-(trimethoxysilyl)propylmethacrylate (TMSPMA) via the silanization. The bonding of multiple TMSPMA monomers on the surface of Fe 3 O 4 nanoparticles renders them as crosslinker. Surfactant-free emulsion polymerization (SFEP) of NIPAm was then carried out with the presence of TMSPMA-modified Fe 3 O 4 nanoparticles at 70 °C in aqueous solution, leading to the formation of thermosensitive PNIPAm-Fe 3 O 4 hybrid microgels crosslinked with Fe 3 O 4 nanoparticles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), dynamic light scattering (DLS) and physical properties measurement system (PPMS) were then used to characterize the resultant hybrid microgels. The experimental results show that the PNIPAm-Fe 3 O 4 hybrid microgels were spherical in shape with a large size distribution and the Fe 3 O 4 nanoparticles were randomly distributed inside the microgels. The PNIPAm-Fe 3 O 4 hybrid microgels were thermosensitive, exhibiting a reversible swelling and deswelling behavior as a function of temperature. The PNIPAm-Fe 3 O 4 hybrid microgels also show superparamagnetic behavior at room temperature (300 K).