Polystyrene Nanospheres Modified with a Hydrophilic Polymer Brush through Subsurface‐Initiated Atom Transfer Radical Polymerization as Biolubricating Additive

Hydration lubrication plays an important role including the cartilage of an organism. Here, polystyrene nanospheres modified with a hydrophilic polymer through subsurface‐initiated grafting as a biolubricating additive is proposed. The material provides good tribological performance when subjected to high load. Compared with surfaced‐initiated grafting polymer brushes, subsurface initiation can form much thicker hydration layers to obtain a lower friction coefficient and better mechanical properties for withstanding prolonged shearing forces with less measurable damage. The polymer brushes penetrate through the covalent network of the polystyrene nanospheres providing a match in mechanical properties between them, so that the additives obtain more excellent lubricity in an aqueous environment under shear pressure, which is expected to become a promising artificial joint biolubricating additive. Compared with surface initiation, subsurface initiation can cause a modulus transition layer and obtain a higher density polymer brush, forming a thicker hydration layer, which can reduce the friction coefficient and the wear rate greatly, and give the subsurface a good mechanical property and provide good carrying capacity, which has potential applications in biolubrication.