Mechanochemically Triggered Grafting of Hydrated Dangling Chains for Enhanced Lubrication in Hydrogel Coatings

Hydrogel coatings endow traditional materials with excellent lubrication performance, meeting the needs of biomedical and lubrication applications. In this work, we propose a lubrication enhancement strategy for hydrogel coatings based on a mechanochemically triggered dangling-chain grafting strategy. Mechanical shear/friction of the covalent network triggers chain scission and simultaneously generates mechanoradicals that initiate the preloading monomer polymerization, grafting a dense, hydrated dangling chain onto the fracture network. The generation of mechanoradicals was verified through DPPH assays, and the stable grafting of dangling chains was proved by wettability, spectrum, modulus, and friction characterizations. The lubricating structure constructed by this method significantly reduces friction and enhances wear resistance, maintaining a stable friction coefficient (CoF ≈ 0.007) over 18,000 cycles. Moreover, when the monomer solution is preloaded within the hydrogel network, friction and wear can trigger in situ regeneration of lubricating dangling-chain layers by a mechanochemical process, achieving long-term self-adaptive lubrication. This strategy also enables surface functionalization by preloading different monomer solutions. It offers a simple, universal route for constructing durable, functional, and adaptive hydrogel coatings.