Synthesis and Properties Study of a Multifunctional Polymethacrylate Viscosity Index Improver

This paper reports on the design, preparation, and characterization of a multifunctional polymethacrylate (PMA) viscosity index improver (VII) that exhibits high oxidative stability and shear stability, which imparts multifunctionality to the viscosity index improver through the introduction of a disulfide pentacyclic ring in lipoic acid. The resulting polymers were added to base oils to investigate their physicochemical and frictional properties. The results demonstrated that, in addition to a significant increase in the viscosity index and high shear stability, the polymers exhibited notable improvements in extreme pressure performance up to 900 N as well as improved antioxidant stability, antiwear, and friction reduction properties. These enhancements were evidenced by a significant reduction in the coefficient of friction and wear volume of the polymers, which decreased by 40% and 92.01%, respectively. Additionally, the polymers exhibited low corrosiveness compared to those of both the base oils and commercial products. Analysis of wear scars revealed that the main formations of protective films were Fe-oxides and Fe-sulfides. This methodology demonstrates the versatility and low corrosiveness of the 1,2-dithiolane-containing viscosity index improver.