Magnetic anisotropy and thermal efficiency of nanocomposite polyethylene grafted with Fe₃O₄nanoparticles synthesized via ring opening metathesis.

This study investigates the magnetic anisotropy and hyperthermic performance of polyethylene-grafted Fe₃O₄ nanocomposites (PE-g-Fe₃O₄ NPs) synthesized via surface-initiated ring-opening metathesis polymerization (SI-ROMP). Surface-functionalized Fe₃O₄ nanoparticles initiated cyclooctene (COE) polymerization, producing polycyclooctene-grafted Fe₃O₄ (PCOE-g-Fe₃O₄) at varying reaction times and Fe₃O₄:COE ratios. Subsequent catalytic hydrogenation generated polyethylene-grafted Fe₃O₄ nanocomposites with improved crystallinity, flexibility, and interfacial adhesion. Controlled polymerization enabled tuning of polymer chain length and Fe₃O₄ loading, facilitating systematic investigation of structure–magnetism relationships. Energy-dispersive X-ray and Fourier transform infrared (FTIR) spectroscopies confirmed surface functionalization with C, O, Si, and Fe signatures, while elemental mapping verified covalent bonding between inorganic and organic domains. Vibrating sample magnetometry (≈300 K) revealed superparamagnetic-like behavior. The polymer shell effectively isolates magnetic domains, and longer polymerization enhances magneto-dipolar coupling, increasing Mₛ, Hc, and anisotropy. SI-ROMP-derived PE-g-Fe₃O₄ nanocomposites thus present a tunable platform for optimizing magnetic and thermal responses, with strong potential in hyperthermia, biomedical imaging, and energy conversion applications.