Unraveling Entanglements Effect on Rate-Dependent Damage in Polymer Networks

Soft polymer networks such as elastomers and gels are increasingly used in soft robotics and biomedical applications due to their remarkable elasticity and deformability. Their capacity to sustain repeated mechanical loading and resist fracture is paramount for reliable operation. These materials derive their elasticity from covalent crosslinks that prevent flow, but limit energy dissipation, leaving networks vulnerable to fracture. Tougher networks can be achieved by incorporating entanglements, transient topological constraints that store, transmit, and redistribute stress across the network. How entanglements relaxation dynamics impacts nonlocal stress transfer and damage delocalization remains a central question in soft matter mechanics. In this work we develop a discrete mesoscale model of a permanently crosslinked elastomer network containing short unentangled elastic chains, and highly viscoelastic entanglements. With this dual-network description we investigate networks rate-dependent fracture behavior by varying both the entanglement degree and loading rate of an in silico single-edge notch specimen. We quantify how the inclusion of entanglements governs the transition between delocalized and localized damage regimes by redistributing stress over large distances. In addition, we demonstrate how entanglements transient nature imparts a rate-dependent coupling between networks viscoelasticity and bond rupture, consistent with experimental observations.