Direct Cross-Linking of Cucurbit[7]uril Pseudopolyrotaxanes to Prepare Slide-Ring Hydrogels

Slide-ring hydrogels have been shown to have exceptional toughness and stretchability. Current designs typically rely on polyrotaxane architectures of cyclodextrin (CD) macrocycles treaded onto polyethylene glycol (PEG) chains. The use of alternative macrocycles to prepare slide-ring hydrogels remains largely unexplored. In this study, we present a cucurbit[7]uril (CB[7]) slide-ring hydrogel prepared from multiblock PEG polymers segmented with guest moieties of varying affinity for binding to CB[7]. Following threading with allyl-modified CB[7] to form pseudopolyrotaxane structures, the side-chains are then covalently cross-linked to yield the slide-ring architecture. The resulting hydrogels exhibit unique mechanical properties modulated by host–guest binding affinity and dynamics. Given the exceptional molecular recognition capabilities of the CB[n] family of macrocycles for diverse guests, using these as alternatives to CDs offers an opportunity to expand the design space for slide-ring hydrogel architectures.