Shear-driven polymerization: critical roles of chemisorption and molecular deformation

Shear force is used to drive chemical reactions in many natural and engineering processes. However, despite the important role of these so-called tribochemical reactions, their fundamental mechanisms are still poorly understood due to challenges associated with directly measuring processes that occur inside a moving contact. To address this, we investigate shear-driven polymerization of molecules adsorbed on silica surfaces, a model system that enables identification of shear-driven reaction pathways. This system is studied using reactive molecular dynamics simulations complemented by pre- and post-sliding surface characterization. The results show that interfacial shear not only accelerates polymerization reactions but opens reaction pathways that are not accessible thermally. Specifically, the simulations reveal that chemisorption and shear-induced deformation of the reactants are critical steps in tribochemical processes. In general, these findings may form the basis for design of systems where shear force can be leveraged to tune or lower the energy cost of chemical reactions.