Rate-dependent fracture mechanics of transient networks*

Soft viscoelastic polymers and gels are commonly used as biomaterials and soft actuators owing to their ability to accommodate large deformations. Their applicability is however often limited by their tendency to abruptly fracture in ways that cannot be predicted by conventional elastic fracture mechanics. Our understanding of the fracturing process in these networks has particularly been hindered by the complex interplay between the viscous dissipation in the bulk and the accumulated damage around the crack tip.

To tackle this question, we explore the condition for a crack to initiate and propagate in transient polymer networks. We used a recently developed Transient Network Theory (TNT) that provides a statistical evolution of a transient network whose topology change as a result of macroscopic deformation and chain reconfiguration via transient crosslinks. This approach is particularly amenable to determine macroscopic measures characterizing the crack driving force. Based on the crack geometry and external loading, we determine the conditions that lead to crack blunting and crack propagation. By determining the interplay of these two mechanisms, we are able to predict fracture process of transient polymer networks with comparison to experiments.