Fatigue-resistant adhesion I. Long-chain polymers as elastic dissipaters

Tough adhesion is often achieved by using inelastic dissipaters. However, inelastic dissipaters fail to enhance adhesion under cyclic loads. Here we achieve fatigue-resistant adhesion by using a particularly simple kind of elastic dissipater: long-chain polymers. Each polymer chain is elastic before rupture. When a single covalent bond of the chain breaks, the elastic energy stored in the entire chain dissipates, amplifying the adhesion energy by the number of links on the chain. So far as the adherends provide the stiffness of an adhered sample, the adhesive can be made of polymer chains of extremely long length. As a proof of concept, we use polyacrylamide hydrogels to adhere two pieces of polyester cloth through topological entanglement. We find that both the adhesion energy and fatigue threshold increase with the polymer chain length and can reach 1400 J/m2 and 300 J/m2, respectively. The measured fatigue threshold of adhesion is linearly proportional to the square root of the chain length, in agreement with the Lake–Thomas model. This fatigue-resistant design can be extended to a variety of adhesion topologies for different adherends and adhesives.