Epoxidized Oleic Acid‐Based Polymethacrylates as Viscosity Index Improvers

This study reports two routes for the synthesis of epoxidized oleic acid (OLA)‐based polymethacrylates. The first one consisted of the synthesis followed by epoxidation of the OLA‐based methacrylate, 2‐(methacryloyloxy)ethyl oleate (MAEO), prior to its radical polymerization. In the second pathway, MAEO was first homopolymerized to afford poly(2‐(methacryloyloxy)ethyl oleate) (PMAEO) and, then, the internal double bonds of the oleate were epoxidized at different yields ranging from 20% to 100%. All polymeric structures were confirmed using 1H nuclear magnetic resonance (NMR), and characterized through size‐exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) analyses. The resulting polymers were then blended at 5 wt.% in a mineral paraffinic oil (MPO) and in a biobased organic triacylglycerol oil (OTO) to be evaluated as viscosity index improvers (VII). The partially epoxidized polymers up to 40% were soluble in MPO. According to a rheological study, the oil‐soluble epoxidized polymers resulting from the epoxidation of PMAEO exhibited a much higher influence on oil viscosities at high temperatures than at low temperatures compared to the low‐epoxidized PMAEO molecular weight obtained by the first strategy. Additionally, the viscosity indices of both lubricating oils were significantly improved with the addition of the epoxidized OLA‐based polymers resulting from the epoxidation of PMAEO, which confirmed their efficiency as VII.