Engineering Double Load-Sharing Network in Thermosetting: Much More than Just Toughening

Current synthetic epoxy thermosets exhibit a trade-off between stiffness and toughness. Despite the urgent demands for highly stiff and tough epoxy thermosetting resins, existing technologies have struggled to attain resins that satisfy this balance. To circumvent this inherent trade-off, a new strategy to obtain a double load-sharing epoxy thermoset network via hierarchical curing process without adding any other filler is proposed. In the epoxy resin bearing acetyl ester side groups cured by an aromatic amine, the "in situ" step-growth phase-separated morphologies and hydrogen-bonding interactions between hydroxyl groups and the ester groups, which endow the resin with high strength and toughness, can be easily controlled by simply tuning the feed ratio of the amine curing agent. Notably, previously unachievable control of mechanical properties is attained, the processing performance is improved, and the product resists hydrothermal aging. The successful application of this strategy provides promising perspectives for construction versatile and high-performance thermosetting.