Elucidating the composition and formation mechanism of slippery films from block copolymers on doped diamond-like carbon surfaces

• Si-doped DLC with functional copolymers reduces friction under boundary conditions. • Stable tribofilms form via strong N–Si bonds without tribochemical reactions. • XPS and ToF-SIMS confirm copolymer adsorption and in-depth tribofilm composition. • Combined experiment and ab initio simulation elucidate tribofilm formation pathways. Silicon-doped diamond-like carbon (Si-DLC) coatings combined with nitrogen-containing block copolymers offer a promising avenue for advanced boundary lubrication. In this study, we investigate the tribological behavior of Si-DLC in the presence of poly(lauryl methacrylate)-block-poly(2-dimethylaminoethyl methacrylate) (PLMA- b -PDMAEMA) to elucidate the formation and stability of tribofilms. Experimental analyses using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) reveal that the polymer strongly adsorbs onto Si-DLC surfaces via robust N–Si bonds. Ab initio simulations further confirm that these N–Si linkages endure sliding and load with minimal bond breakage or polymer fragmentation. Importantly, the tribofilm’s formation is driven primarily by polymer adsorption and compression, rather than by tribochemical reactions. This adsorption-driven pathway results in significant friction reduction and enhanced wear resistance, highlighting the critical role of silicon doping in promoting strong interfacial anchoring of the functionalized polymer. The findings establish that PLMA- b -PDMAEMA acts as both a lubricant film former and a protective barrier, paving the way for new strategies to optimize boundary lubrication under harsh conditions. Overall, this study demonstrates how the synergy between functionalized polymers and doped DLC coatings can be harnessed to achieve superior tribological performance, thereby broadening the applicability of polymer-based lubrication solutions across diverse mechanical systems.