Terminal group engineering of polyether amines: Overcoming steric hindrance for enhanced adsorption and lubrication performance on iron surfaces

Polymers’ advantage of multiple adsorption sites in solid-liquid adsorption is typically constrained by their inherent steric hindrance. The research focuses on optimizing polymer adsorption on iron surfaces through terminal polar group engineering to conquer steric hindrance and boost solid-liquid interfacial adsorption efficiency. Three polyether amine derivatives are synthesized: ATPE-MA (carboxyl/amide), ATPE-P2C (pyridyl/cyano), and ATPE-NC (amide/alkyl). In-situ monitoring and theoretical calculations show that terminal polar groups synergize with multi-adsorptive sites on the polymer backbone via a “molecular clamping” effect, overcoming steric hindrance. ATPE-MA’s carboxyl terminal drives planar adsorption through strong coordination, forming a 1.7 nm dense film with the highest adsorption energy. By contrast, ATPE-NC’s weak polarity causes partial chain detachment, leading to a 0.4 nm loose layer. The evaluation of lubrication performance investigates the macroscopic performance of adsorption properties in industrial applications: stable adsorption films trigger tribochemical reactions to form iron-based/amorphous carbon composite films for continuous lubrication. ATPE-MA’s superior adsorption promotes more interfacial molecular aggregation and tribofilm formation, thus has the best lubrication performance. This cross-scale analysis of “molecular engineering-adsorption behavior-macroscopic performance” offers new approaches for designing high-adsorption functional molecules in surface engineering.