Synthesis of Crosslinked Biopolyesters Catalyzed by Natural Amino Acids

Epoxidized sunflower oil (ESO), derived from waste sunflower oil (WSO), was copolymerized with various biobased cyclic anhydrides via ring-opening copolymerization (ROCOP) reaction to produce highly crosslinked polyesters. This catalytic synthesis was performed by a metal-free catalyst system formed by natural amino acid (L-glutamic acid) and tetrabutylammonium iodide (TBAI). The resulting bio-polyesters, obtained as jelly-like disks, were thoroughly characterized using multiple techniques such as FT-IR, TGA, and DSC. The presence of a crosslinked network in the biobased polymers was assessed by dynamical mechanical analysis (DMA) and at room temperature the rubbery state of crosslinked materials was observed. These materials demonstrated complete degradability when treated with a 1 M aqueous sodium hydroxide solution. In addition, density functional theory (DFT) calculation was employed to elucidate the polymerization mechanism, focusing on the activation stage of the polymerization process. This study provides valuable insights into the catalytic efficiency and mechanistic details of the polymerization process, highlighting the potential of sustainable, metal-free catalysts for producing degradable biopolyesters.