Magnetic Nanoparticles Improve Flow Rate and Enable Self-Healing in Covalent Adaptable Networks

Covalent adaptable networks (CANs) combine the mechanicaland chemicalstability of thermosets with the reprocessability of thermoplasticsthrough the incorporation of stimuli-responsive dynamic crosslinks.To allow for processing through induction heating, we have createdassociative CANs that include fillers in the polymer matrix for efficientheat transfer. While the inclusion of inorganic fillers often decreasesflow rate in CANs and complicates reprocessing of the material, thepresence of Fe3O4 nanoparticles had no detrimentaleffect on flow behavior in a vinylogous urethane vitrimer, an observationwe attribute to the catalytic nature of nanoparticles on the dynamicexchange chemistry. We employed two methods of nanoparticle incorporation:blending bare nanoparticles and crosslinking chemically modified nanoparticles.The vitrimers with covalently crosslinked nanoparticles exhibiteda decreased relaxation time compared to those with blended nanoparticles.The magnetic character of the Fe3O4 nanoparticlesenabled self-healing of the vitrimer composite materials upon exposureto an alternating electromagnetic field during induction heating.

Automated summary

Covalent adaptable networks (CANs) combine the stability of thermosets with the reprocessability of thermoplastics through the incorporation of dynamic crosslinks. In this study, we incorporated Fe3O4 nanoparticles as fillers in a vinylogous urethane vitrimer to facilitate induction heating processing. Despite the common decrease in flow rate and reprocessing difficulty caused by the inclusion of inorganic fillers, the presence of Fe3O4 nanoparticles did not affect the flow behavior of the vitrimer, possibly due to the nanoparticles' catalytic effect on dynamic exchange chemistry. Two methods of incorporating the nanoparticles were employed, and the vitrimers with covalently crosslinked nanoparticles exhibited a shorter relaxation time compared to those with blended nanoparticles. The magnetic character of the Fe3O4 nanoparticles enabled self-healing of the vitrimer composite materials during induction heating.