Interfacial Dynamics and Mechanical Properties of Substrate-Supported [c2]Daisy Chain Networks

Mechanically interlocked networks (MINs) comprise molecular components linked through mechanical bonds, imposing topological constraints that prevent fragment separation. Despite extensive experimental works on this intriguing material, theoretical investigations remain limited. Herein, we employ coarse-grained molecular dynamics simulations to explore the structure, interfacial dynamics, ring sliding, and mechanical properties of substrate-supported MINs thin films composed of [c2]daisy chains, where the effects of potential sliding distances (n), cross-linking degree (c), interfacial cohesive strength (ϵ_ps), and temperatures (T) are systematically explored. Our results show that stronger dynamic confinement occurs near the substrate with increasing ϵ_ps, particularly at lower T. Conversely, lower ϵ_ps (≤0.5) enhances the dynamics of the [c2]daisy chain near the substrate, resembling free-surface behavior. Interestingly, ring molecules display slower dynamics than axle chains, whose mobility strongly depends on proximity to the binding site, consistent with previous experimental studies. Conformational behavior remains largely unaffected by variations in ϵ_ps, T, and c, while an increase in n slightly enhances chain dynamics, increasing the radius of gyration (R_g). Pull-out tests reveal three stages in explaining the ring sliding mechanism. Initially, the ring tilts on the axle under tension without dissociation due to strong binding interactions. Subsequently, the ring dissociates from the binding site, leading to a rapid increase in sliding distance. Finally, the sliding distance reaches a plateau that matches the n value of the model. The durations of the latter two stages are significantly influenced by c. Higher c promotes crazing fiber formation, triggering an earlier onset of the second sliding stage, and increasing plateau stress during pull-out. These findings offer molecular-level insights into [c2]daisy chain MIN behavior, providing a foundation for future research on diverse MIN architectures and their applications in smart and adaptive materials.