Formation Principles and Failure Mechanisms of Cyanate Ester Curing Networks

Cyanate ester (CE) resins are high-performance matrix materials extensively utilized in extreme environments owing to their exceptional thermal stability and superior dielectric properties. However, the highly cross-linked network based on triazine rings also leads to intrinsic brittleness, severely limiting their broader applicability. The molecular-scale failure mechanisms remain insufficiently understood, partly due to the challenge of constructing accurate molecular models. This study overcomes these limitations by integrating molecular dynamics simulations with experimental validation. We developed a high-precision cross-linking algorithm incorporating reversible dimer metastable intermediates to form stable triazine rings and innovatively combined the polymer consistent force field with a Morse potential to simulate bond rupture during network failure. The resulting model predicts key performance parameters with less than a 3% error. Network formation is shown to proceed through three distinct kinetic stages: rapid oligomer formation, competitive network growth, and network integration/densification. More importantly, this work reveals a failure mechanism: although fracture is macroscopically brittle, it involves significant “microplasticity” at the molecular scale. The process is deconstructed into five characteristic stages with energy evolution analysis uncovering a dynamic equilibrium between elastic storage and dissipation via chain slippage, topological reorganization, and bond rupture/reformation. We conclude that macroscopic brittleness fundamentally results from the concentrated release of energy accumulated through numerous localized microplastic dissipation events.