Friction Modulation via Ring-Size Engineering of Polyrotaxanes for Synergistically Tough and Low-Hysteresis Ionogels

Conventional tough ionogels designed via energy-dissipative strategies (sacrificial bonds and double networks) face an inherent trade-off between mechanical robustness and recoverability. Here, we present a topological engineering approach utilizing ring-size-tuned polyrotaxanes (PRs) with γ-cyclodextrin (γ-CD) sliding rings to resolve this conflict. By steric hindrance-modulated synthesis, γ-polyrotaxane (γ-PR) with bigger size of ring cavity and lower sliding friction was integrated into a poly(acrylic acid) (PAA) ionogel. The resulting ionogels achieved high stretchability of 768%, high toughness (work of fracture) of 296 kJ m –3, and low hysteresis (residual strain ∼4.5%), surpassing most gels cross-linked by polyrotaxanes. Furthermore, single-molecule force spectroscopy and molecular dynamics simulations of α-PR and γ-PR systems revealed that the γ-cyclodextrin with a larger ring size possessed higher dynamics and lower ring-axle friction, enabling smoother sliding motion to realize better stress homogenization and minimized energy dissipation between rings and axles. Our work establishes ring-size modulation in slide-ring architectures as a paradigm-shifting strategy to overcome the toughness-recovery trade-off, advancing polyrotaxane-cross-linked gels toward commercial applications.