From bonds to breaks: multiscale perspectives on polymer network fracture

Fracture in polymer networks arises from complex, multiscale phenomena spanning molecular bond rupture to macroscopic crack propagation. This review summarizes recent theoretical and computational advances that deepen our understanding of polymer network fracture. We trace the evolution from classical theories, such as Griffith’s energy balance and the Lake-Thomas theory of chain scission model to recent frameworks incorporating nonlocal energy dissipation, topological defects, and loop-opening mechanisms. Emphasis is placed on how network structure, entanglement, and architectural heterogeneities influence fracture toughness. To complement these theories, we examine a wide range of simulation strategies, including all-atomic molecular dynamics, coarse-grained models, mesoscale network representations, and continuum mechanics. These simulations reveal the molecular origins of void nucleation, craze formation, and crack advancement in materials ranging from glassy polymers to double networks and nanocomposites. Additionally, we discuss the quasistatic and dynamic mesoscale models employed to study the influence of network connectivity and spatial heterogeneity as critical links between molecular mechanisms and macroscopic fracture. At the continuum scale, cohesive zone modeling, eXtended Finite Element Method, and damage-based are discussed to simulate macroscopic crack growth and complex fracture patterns. Together, these multiscale approaches provide mechanistic insights and design principles critical for tougher, more resilient polymeric materials. Finally, we discuss emerging opportunities in dynamic scale-bridging, machine learning integration, and the design of defect-tolerant architectures.