Phase-Separated Elastomers with Interfacial Dynamic Cross-Links: Reconciling the Modulus–Toughness Conflict While Integrating Recyclability and Creep Resistance

Polymer networks typically find themselves trapped in two opposing trade-offs: enhancing stiffness comes at the expense of toughness, while introducing recyclability compromises creep resistance. In this study, we present a design principle for phase-separated elastomers that breaks the modulus–toughness correlation while achieving both recyclability and improved creep resistance. These elastomers (TGE) are fabricated by dispersing a densely cross-linked copolymer (TG) of thioctic acid and glycidyl methacrylate into epoxidized natural rubber (ENR), followed by an interfacial carboxyl-epoxy reaction that enables the cross-linking of ENR with the dispersed TG domains via β-hydroxy ester linkages. As the TG content increases, the cross-linking density of TGE gradually rises, allowing the mechanical properties to be tuned over a broad range. Counterintuitively, the toughness of TGE improves continuously with cross-linking density. The underlying energy dissipation mechanisms in the TGE stem from the synergistic effects of the phase-separated structure and interfacial cross-links. Furthermore, the transesterification of β-hydroxy esters endows TGE with recyclability, while the phase-separated structure enhances creep resistance by imposing greater constraints on chain mobility. These attributes make TGE highly attractive as shape memory polymers, offering high energy density, high shape-fixity and shape-recovery performance, and the ability to be plastically reconfigured into geometrically complex objects.