Understanding the formation mechanism of the adsorbed film formed by additives is critical to clarify the boundary lubrication characteristics. In this study, we present a dual-functional molecular design strategy that enables simultaneous friction reduction and direct visualization of adsorbed films using fluorescence microscopy. 1-Pyrenemethyl laurate, and pyrene-labeled poly( n -octyl methacrylate) were synthesized and evaluated. Fluorescence imaging revealed that both organic friction modifiers (OFMs) adsorbed onto steel surfaces, with adsorption amount and coverage increasing with concentration. 1-Pyrenemethyl laurate exhibited multilayer adsorption at high concentrations and a tendency to accumulate in surface depressions, while the polymer showed more homogeneous and stable adsorption on the surface. Friction tests showed that both OFMs effectively reduced the coefficient of friction in boundary lubrication. These findings demonstrate the effectiveness of fluorescence-labeled OFMs for analysis of adsorption dynamics and offer a new strategy for the design of advanced lubricant additives. • Dual-function OFMs were designed to enable both friction reduction and direct in situ visualization of adsorbed films via fluorescence microscopy. • Spatial distributions of adsorbed films were observed and analyzed. • Pyrenemethyl laurate showed concentration-dependent multilayer adsorption and localized accumulation in surface depression. • Pyrene-labeled PMA formed uniform and shear-resistant adsorbed films.
Song et al. (Sun,) studied this question.