Interfacial Fracture of Soft Polymer Networks: Revisiting Gent's Picture

Soft, tough polymer networks underpin wearable electronics, soft robotics, and flexible interfaces, yet the microscopic origins of their interfacial fracture toughness (i.e., adhesion energy) remain unresolved. In this talk, I will examine the competing roles of bulk viscoelasticity and molecular-scale damage on interfacial fracture by combining rate- and temperature-controlled peel tests with spatially resolved measurements of bond scission using fluorogenic mechanophores. I will correlate adhesion energy with linear viscoelastic properties (e.g., network relaxation times) and mechanophore-derived maps of damage adjacent to peeled surfaces across a broad matrix of peeling rates and temperatures. The results will identify regimes where conventional linear-viscoelastic fracture theories—which attribute dissipation solely to bulk relaxation—fail to predict adhesion energy because irreversible molecular damage contributes significantly to dissipation within the fracture process zone in a chemistry- and rate-dependent manner. Building on Gent's seminal picture, I present an experimentally constrained framework that links network timescales, the emergence and extent of the damage zone, and measured adhesion energy, and discuss design strategies for polymer networks with tunable adhesion and damage tolerance.