Dual dynamic network structures of recyclable epoxy resins with high strength and toughness via sacrificial hydrogen-bonding clusters and imine bonds: surpassing the strength-toughness trade-off

Thermosetting epoxy resins with high strength , high toughness, and recyclability are strongly sought after, but due to crosslinked structure, balancing strength and toughness and achieving degradation and reprocessing of resins is a challenge. Enhancing strength without compromising toughness during designing recyclable epoxy resin is a challenging task. Herein, a solution is demonstrated where isofluorodioxanone diisocyanate (IPDI), Poly (propylene glycol) bis(2-aminopropyl ether) (D230), and naturally occurring vanillin synthesized a novel imine-functionalized epoxy monomer (IDV-EP), and cured with diamino-diphenylmethane (DDM), 2-(4-aminophenyl)-1H-benzimidazol-5-amine (APBIA) and 4, 4-diamino benzoyl triphenylamine (DABA), respectively, for the purpose of building different contents of the sacrificial hydrogen-bonding clusters (SHBC) in topological network structures. As the hydrogen-bonding (H-bonding) binding energy of the crosslinked network increases, the strength and toughness of the resin were increased concurrently, SHBC was demonstrated to be a feasible method to achieve the strength-toughness trade-off of thermosets, in which IDV-EP-DABA illustrated a tensile strength of 90 MPa, an elongation at break of 16.5%, as well as toughness of 9.73 MJ/m 3 , which was higher than that of the ordinary bisphenol A-type epoxy thermosetting resin (DGEBA/DDM) by 1.8, 3.7 as well as 6.7 times, respectively. Furthermore, the covalent adaptive networks (CANs) formed by imine bonds provide the resins with effective capabilities for swift degradation (rapid degradation in acid/solvent, room temperature and static conditions) and reprocessing (only a slight decrease in the mechanical properties after hot pressed at 180°C/10 MPa for 15 minutes) , showcasing promising prospects for sustainable utilization.