Molecular structure insight into the lubricating performance of heterocyclic ester oil and their film-forming interaction

Ester oils are characterized as an important component of high-performance lubricants by virtue of their unique physicochemical properties and high degree of molecular design. Not all ester oil molecules exhibit lubricating and load-carrying properties, which are influenced by the molecular structure. Herein, ester oils containing heterocyclic diester structure were designed and synthesized, and alkyl diester (1088) were selected as reference samples. By comparative exploration of viscosity-temperature properties, thermal stability and adsorption performance, molecular configurations with low steric hindrance are more conducive to the adsorption stability of polar ester-based molecules at metal interfaces. Compared to the control sample, the synthesized ester oil exhibits certain friction-reducing and anti-wear properties, whose performance is affected by the position of substituent in the case of the same ester structure. The conformation of the substituent group in a position adjacent to the ester group contributes more to lubrication stability. This work provides theoretical guidance for the relationship between the molecular structure of high-performance ester oil and the structural evolution of its interfacial tribofilm.