Synergistic Dual Slip-Link Toughening of a Water-Rich Double Network Hydrogel Combining Slide-Ring and Highly Entangled Networks.

Slide-ring network (SRN) hydrogels derived from ring-crosslinked polyrotaxanes exhibit exceptional mechanical properties attributable to a pulley effect, whereby mobile-ring crosslinks redistribute tension under deformation through a slip-link mechanism. However, SRN hydrogels weaken severely upon swelling in water, limiting their utility at high water content ( > 90 wt.%). Here, two distinct physical slip-link mechanisms are combined in a highly entangled slide-ring double network (HESRDN) hydrogel: the pulley effect of a polyrotaxane slide-ring network and the entangled chains of a sparsely cross-linked polyacrylamide network. HESRDN is prepared by photopolymerization of acrylamide/N,N'-methylenebis(acrylamide) within a partially swollen slide-ring hydrogel. The dual slip-link architecture synergistically strengthens and toughens the hydrogel far beyond the sum of the component networks, yielding high work of fracture (1275 kJm-3), toughness (2020 Jm-2), and near-complete reversibility (99.7%) at > 91 wt.% water. HESRDN withstands continuous friction for over 12 h without rupture, compared to minutes for the SRN and 5 h for the HEN component networks, reflecting the unique capacity of the dual slip-link architecture to delocalize and redistribute stress under sustained mechanical loading.