A catch bond mechanism with looped adhesive tethers for self-strengthening materials

Abstract

The lifetime of chemical bonds shortens exponentially with force. Oddly, some protein-ligand complexes called catch bonds exhibit a sharp increase in lifetime when pulled with greater force. Inventing catch bond interfaces in synthetic materials would enable force-enhanced kinetics or self-strengthening under mechanical stress. Here, we present a molecular design that recapitulates catch bond behavior between nanoparticles tethered with macromolecules, consisting of one looped and one straight tether linking particles with weak adhesion. We calibrate the loop stiffness such that it opens around a target force to enable load-sharing among tethers, which facilitates a sequential to coordinated failure transition that reproduces experimental catch bond force-lifetime curve characteristics. We derive an analytical relation validated by molecular simulations to prove that loop and adhesion interactions can be tailored to achieve a spectrum of catch bond lifetime curves with this simple design. Our predictions break new ground towards designing tunable, catch-bond inspired self-strengthening materials.