Sawtooth-to-brittle transition in cubane architectures by dimensional constraints

Recently synthesized cubane-derived scaffolds offer an unprecedented platform to explore dimensionally-constrained mechanical behavior in covalently bonded nanomaterials. Here, the combined effects of structural dimensionality and temperature on the uniaxial tensile behavior of cubane-derived architectures are systematically investigated using classical molecular dynamics simulations. The results demonstrate that mechanical response, deformation pathways, and fracture mechanisms are predominantly governed by structural dimensionality rather than local bond strength alone. The 1D cubane thread exhibits pronounced sawtooth-like stress–strain fluctuations, reflecting intrinsic structural instabilities arising from sequential C-C bond rupture and partial structural reconstruction. The 2D cubane sheet displays moderate stress oscillations and exceptional extensibility, with deformation dominated by buckling-assisted energy dissipation and out-of-plane structural accommodation. In contrast, the 3D cubane framework exhibits abrupt stress attenuation characteristic of brittle fracture, governed by highly-constrained load transfer within the rigid, fully connected cubic network. Key mechanical parameters, including Young’s modulus, tensile strength, and fracture strain, exhibit strong temperature dependence while preserving a consistent stiffness hierarchy of 3D > 2D > 1D. These findings establish a mechanistic structure–property relationship linking dimensional confinement, thermal activation, and fracture kinetics in cubane-based materials, and provide guidance for the rational mechanical design of cubane-derived scaffolds in nano-reinforced composites, flexible electronics, and energy-absorbing systems.