Tough, Fatigue-Resistant Elastomer Networks via Dynamic Interactions

Elastomers commonly experience failure due to crack propagation when subjected to external loads. Currently, significant focus has been placed on enhancing the resistance to crack propagation. Various methods exist to improve resistance to crack growth under monotonic loads, which is characterized by fracture energy (Gc) but hardly contributes to crack propagation resistance under cyclic loads, which is characterized by intrinsic fracture energy (Γ0). In this work, we demonstrate an effective strategy to simultaneously improve Gc and Γ0 by dynamic interactions. Diazo compounds, as model cross-linkers, are used to design covalent cross-linking networks and dynamic disulfide bond networks. Experimental results show that covalent cross-linking networks are highly flaw-sensitive, while dynamic disulfide bond networks are insensitive to flaws. As covalent cross-linking networks are progressively replaced by dynamic disulfide bond networks, Gc and Γ0 increase to 770 and 2800 J/m2, respectively. This enhancement is attributed to stress deconcentration through dynamic interactions. The strategy presented in this work provides an approach to simultaneously improve crack propagation resistance under monotonic and cyclic loads, opening an enormous design space for general applications.