Molecular Mechanism of Silicone Network Unbinding: Visco-Elastic Modes and Fracture upon Tensile Testing

We report on tensile testing of atomistic simulation models mimicking silicone resins. To this end, we extend previous studies on silicone hardening and network formation (Polymers 2025, 17, 2619) to molecular dynamics simulations of the atomic-scale processes that account for elastic behavior, visco-elastic and plastic deformation. This encompasses Si–O bond scission and reformation, thus giving rise to siloxane network reorganization upon yielding, which implies both slipping of molecular chains and chemical modifications in terms of changing siloxane cross-linking. Based on graph theory, we discriminate percolating siloxane strands and elucidate the interplay of large per-atom stress in these load-bearing parts of the polymer network and heterogeneity of atomic displacements to dissipate local stress. On this basis, findings from atomic-scale characterization are discussed in the context of bulk polymer mechanical characteristics such as maximum stress, plasticity and fracture energy (4.7 ± 0.9 J/m2).