Strategic weakening for holistic strengthening: overstrain-driven synchronous strengthening-toughening in sustainable rubber via “weak” non-covalent networks

Abstract

The pursuit of sustainable rubbers with exceptional mechanical robustness is hindered by intrinsic paradoxes: dynamic covalent networks enable recyclability but compromise mechanical performance, and high-cohesive-energy non-covalent networks are constrained by a fundamental trade-off between strength and ductility. Herein, we introduce a strain amplification paradigm dominated by the purposeful design of non-covalent networks—an approach that strategically engineers stress-bearing pathways through the synergy of reduced cohesive energy and hierarchical interactions. By modulating the cohesive energy of hydrogen-bonding networks in epoxidized natural rubber (ENR), we activate an overstrain-driven stress redistribution mechanism, seamlessly coupling with strain-induced crystallization (SIC) to achieve overstrain-driven strengthening and toughening (ODST)—a counterintuitive yet highly effective strategy for achieving macroscopic robustness. Moreover, implementing the ODST principle in a sustainable rubber via a hierarchy of non-covalent interactions (4U1N-2) yields record-breaking mechanical performance, surpassing state-of-the-art reprocessable rubbers, with a tensile strength of 19.36 MPa, an elongation at break of 1529%, and a toughness of 106.67 MJ m⁻³. Notably, 4U1N-2 retains substantial mechanical properties after reprocessing, exhibiting performance that exceeds the original properties of most reprocessable rubbers. Moreover, it demonstrates outstanding self-healing capabilities, with strength and elongation at break recovering to 88% and 85%, respectively. This work pioneers a “strategic weakening for holistic strengthening” principle, providing a universal framework for designing high-performance, sustainable elastomers.