Why is Mechanical Fatigue Different from Toughness in Elastomers? The Role of Damage by Polymer Chain Scission

Although elastomers often experience 10-100 million cycles prior to failure, there is currently a limited understanding of their resistance to fatigue crack propagation. We use soft and tough double-network elastomers tagged with mechanofluorescent probes to understand the role of damage by sacrificial bond scission on their mechanical durability and fracture toughness. Damage accumulation and localization ahead of the crack tip depend on the areal density of sacrificial bonds, as well as on the applied load (i.e., cyclic or monotonic). This information serves to engineer fatigue resistant elastomers, understand fracture mechanisms, and reduce the environmental footprint of the polymer industry.