Quantitative Structure Tribo-Ability Relationship (QSTR) Study of Polyimide-induced Alignment Superlubricity System Based on CoMSIA Modeling

Abstract This study investigates the tribological properties of 43 isotropic organic compounds (e.g., alcohols, aldehydes, acids, esters, and halogenated hydrocarbons) as lubricants in a polyimide (PI)-Si₃N₄ friction pair system. A comparative molecular similarity indices analysis (CoMSIA)-QSTR model was developed to analyze the relationship between lubricant molecular structures and system performance. The CoMSIA-QSTR model generated 3D contour maps by correlating molecular field characteristics (hydrophobicity, hydrogen bond donor/acceptor fields) with tribological performance. These maps reveal that hydrophobic long chains and hydrogen bond donors/acceptors in friction-reduction favorable regions correlate with low friction coefficients, consistent with experimental observations. Small molecules with strong hydrogen bond donors (e.g., hydroxyl or carboxyl groups) form hydrogen bonds with PI’s carbonyl and imide groups, promoting lubricant alignment and achieving superlubricity (COF < 0.005). Long carbon chains adsorb onto PI surfaces via dispersion forces, facilitating ordered molecular layer formation at the interface. Polar molecules align more readily under PI’s polarity-driven induction, further enhancing friction reduction. The CoMSIA model demonstrated robust predictive capability (q² >0.65, r² >0.70) and was generalized to ionic liquids (e.g., imidazolium salts).