Ring Sliding-Bond Scission Interplay Affects Toughening in Mechanically Interlocked Networks

Abstract

Mechanically interlocked networks (MINs) built from [2]rotaxane cross-linkers combine high extensibility with enhanced toughness, yet how the interplay between ring mobility and bond scission influences their mechanical responses remains unclear. Here, we employ coarse-grained molecular dynamics simulations to investigate the deformation mechanisms of MINs with varying bond strength, strain rate, and graft density, where a crossover is observed in the deformation mechanism as bond strength increases. Specifically, the weak cross-links lead to scission-dominated deformation with negligible ring sliding, whereas MINs with strong cross-links exhibit profound ring sliding and inhibited bond scission, contributing to the enhanced toughness. Moreover, bond scission and ring sliding exhibit a strain-rate response with the lowest rate favoring scission over sliding, while reducing graft density delays the onset of both processes. These findings provide molecular insights for optimizing MIN mechanics by balancing movable-junction dynamics and cross-link stability.