Sustainable Synthesis of Bio-Based Oligoesters via ROCOP Reaction of Epoxidized Vegetable Oils with Cyclic Anhydrides Catalyzed by Ionic Liquids

This study presents an efficient method for producing biobased oligomers from waste cooking oils (WCOs), a renewable and sustainable feedstock. Epoxidized vegetable oils derived from olive (EOO), sunflower (ESO), and grape seed (EGSO) oils were copolymerized via ring-opening copolymerization (ROCOP) with cyclic anhydrides such as phthalic and maleic anhydride. The reaction was catalyzed using five ionic liquids as organocatalysts, combined with tetrabutylammonium iodide as a cocatalyst. Among them, 1-butyl-3-methylimidazolium (IL1) showed the highest activity, allowing quantitative conversion at 80 °C within 1 h. The resulting oligomers (Mn(exp) = 1021–1732 Da) were characterized by NMR, FT-IR, GPC, and TGA. A mechanistic study supported by NMR and DFT calculations revealed that ionic liquids promote epoxy ring opening through hydrogen-bond stabilization. Overall, the work highlights ionic liquids as effective catalysts for the rapid synthesis of biobased oligoesters via ROCOP.