Biomolecular "lock-key" model-inspired cage/benzene ring structure chain-extension matching strategy for high performance of linear waterborne polyurethane toward application in recyclable soft robotics.

To overcome the intrinsic limitation of linear waterborne polyurethanes (WPUs) in balancing chain-segment flexibility and mechanical robustness, and to meet the high requirements for matrix materials in soft robotics, we propose an innovative chain-extension matching strategy inspired by the biomolecular "lock-key" model. A novel cage-like chain extender (IC) was designed and synthesized as the "lock", while three structurally distinct chain extenders served as the "key" respectively to construct corresponding linear WPUs. Systematic investigations reveal that differences in the matching effects arising from different chain extender combinations significantly influence both the microstructure and the macroscopic properties. Notably, the strong geometric and interaction matchability between IC and 4, 4'-diaminodiphenylmethane enables the formation of distinct microphase-separated structures, stable viscoelastic networks, and efficient energy dissipation pathways, thereby imparting the resulting elastomer (IC-MDA) an exceptional balance of tensile strength (52.9 MPa) and toughness (211.7 MJ m-3). Furthermore, incorporating 1 wt% monolayer graphene into IC-MDA establishes a continuous thermal conduction network, enabling IC-MDA-based actuators to achieve an 83.9% deformation recovery rate under a 40 g load. This work not only establishes a generalizable molecular design principle for overcoming the limitations of traditional chain extenders but also provides novel strategies for developing high-performance WPUs toward next-generation soft robotics.