Magnetic Hyperthermia to Promote Acrylamide Radical Polymerizations

Radical polymerization is widely employed for the preparation of advanced materials with controlled properties and responsiveness. Depending on the radical initiator, different stimuli can trigger the beginning of the reaction. This work presents an innovative approach that exploits the heat released by magnetic nanoparticles when they are excited by an alternating current (AC) magnetic field to induce radical polymerizations. In particular, the use of cobalt ferrite (CoFe2O4) nanoparticles is explored for the preparation of polyacrylamide hydrogels, chosen as a model material to demonstrate the strategy. Magnetic and mechanical characterizations reveal that the materials possess properties similar to those of samples prepared by classical thermal polymerization. Indeed, magnetic hyperthermia is a versatile tool for remote temperature control in a localized space that can have different applications. An example is represented by its use for a selective volume polymerization in a thermosensitive environment, overcoming classical problems of both bulk thermal polymerization (e.g., not applicable in delicate environments) and photopolymerization (e.g., poor light penetration). The obtained results pave the way also for production of non-magnetic materials, in which magnetic nanoparticles are first concentrated in a small solution volume (by a permanent magnet) and then exploited to activate the polymerization of the whole material (by an AC magnetic field).