Nanoparticle Assembly Drives Magnetic Hyperthermia in Semi-Crystalline Polymers

We investigate how the assembly of magnetic nanoparticles embedded in a semi-crystalline polymer governs heat generation when submitted to a high-frequency alternating magnetic field by simultaneously monitoring temperature and structural anisotropy through infrared thermography and time-resolved ultra-small-angle X-ray scattering, respectively. A polypropylene matrix is used as a host system to disentangle intrinsic magnetic heating from structural contributions, thereby isolating the additional heat generated by dipolar chain formation above the polymer melting point during successive heating cycles. In contrast, reorienting the chain axis perpendicular to the applied field is found to significantly reduce heat generation. These in situ measurements are complemented by X-ray tomography and scanning electron microscopy experiments, providing a comprehensive view of the underlying mechanisms. Overall, this work establishes a direct relationship between nanoparticle organization and hyperthermia performance, opening new routes for the rational design of functional nanocomposites.