Superparamagnetic  iron oxide nanoparticle – vitrimer nanocomposites: Reprocessable and multi-responsive materials

The field of stimuli-responsive soft materials is rapidly evolving, particularly with recent advances in the design and fabrication of magnetic soft materials. Magnetically responsive elastomers, which incorporate magnetic particles into an elastomeric matrix, exhibit rapid and reversible actuation in the presence of a magnetic field, making them highly suitable for the development of flexible, remote-controlled soft robots. However, conventional crosslinked elastomer materials often lack recyclability and the versatile properties associated with vitrimer materials. Vitrimers, which are dynamically crosslinked polymers, can be reprocessed upon heating and offer valuable features such as recyclability and self-healing. In this study, we developed vitrimer nanocomposites by incorporating 5 to 15 wt% superparamagnetic iron oxide nanoparticles (SPIONs) into a vinylogous urethane vitrimer matrix, yielding materials that exhibit both thermal and magnetic responsiveness. Furthermore, a novel acetoacetylated ligand with a phosphonic acid anchoring group was utilized to modify the surface of SPIONs, enhancing their stability and enabling their covalent linking to the vitrimer matrix. The crosslinking of the nanoparticles to the matrix improves the mechanical properties, including increased tensile stress and strain. Since the nanoparticles are covalently bound to the matrix, the resulting material can be reprocessed and recycled without compromising the uniform distribution of SPIONs, thereby promoting a closed-loop cycle of reuse and recycling while preserving the mechanical and magnetic properties of the nanocomposites. The integration of SPIONs into vinylogous urethane vitrimers results in the development of sustainable advanced materials with enhanced stability and functionality, highlighting their potential across various applications.