Thermally Responsive Ionic Liquid Catalyst Decoupling Processing Window and Dynamic Exchange in Epoxy Vitrimers

Epoxy vitrimers are promising sustainable thermosets, yet their practical application is hindered by an inherent conflict rooted in the typically required catalysts of high activity. Such catalytic activity, while enabling dynamic bond exchange at elevated temperatures, also triggers premature curing and creep failure, narrowing the processing window and compromising dimensional stability. Herein, we report a thermally responsive ionic liquid catalyst (ILC) that resolves this tradeoff through a non-covalent ion-pair strategy. Constructed by equimolar neutralization of phenol with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), the liquid ILC allows for rapid, homogeneous mixing with the resin formulation, thereby eliminating the dispersion issues inherent to conventional solid catalysts like TBD, avoiding prolonged dissolution times and inhomogeneous network formation. It leverages reversible proton transfer to achieve temperature-gated catalytic activity. Ion-pair interactions passivate TBD at ambient and service temperatures-extending gel time at 80°C to 56.6 min (vs. 17.5 min for free TBD) and suppressing creep-while dissociating above 180°C to restore catalytic activity, as evidenced by a two-regime Arrhenius behavior in stress relaxation. This enables multiple hot-press reprocessing cycles with high property retention. The ILC thus effectively decouples processing window, creep resistance, and reprocessability, offering a practical pathway toward sustainable epoxy vitrimers.