Superlubricious Surfaces Through Surface Attached Hydrogels Obtained by C,H‐insertion Crosslinking

The friction behavior of surfaces is investigated which are coated with surface‐attached hydrogel layers inspired by the structure of natural synovial joints. Photoinduced C,H insertion chemistry is used to form polymer networks from hydrogel precursor polymers and simultaneously link them to both sliding partners. As the crosslinking is performed in the dry state and all polymer chains are covalently bound to the surface, the hydrogel layers can only swell in one direction leading to strong chain stretching. This confinement leads to surfaces with ultralow adhesion and strongly reduces friction. The incorporation of charges and the addition of shear‐thinning polymers to the water phase allows for the generation of friction systems having coefficients of friction of µ = 0.002-0.001, thus reaching superlubricity and even surpassing the values reported for the properties of the natural model.