Efficient Activation of Dimethyl Carbonate to Synthesize Bio-based Polycarbonate by Eco-friendly Amino Acid Ionic Liquid Catalyst

Abstract Herein, an efficient synthetic strategy for synthesis of bio-based polycarbonate has been developed by using tetramethylammonium-based amino acid ionic liquids (AAILs) as catalysts for the melt polymerization of isosorbide (ISB) and dimethyl carbonate (DMC). These AAILs exhibited outstanding catalytic activity towards DMC, enabling the selectivity of carboxymethyl intermediates greater than 99%. By modifying the anionic structure of AAIL catalysts, the conversion of ISB and the molecular weight of PIC could be remarkably improved. Tetramethylammonium arginine ([N1111][Arg]) showed the highest catalytic activity due to its multiple active sites and high basicity. Combining experimental results and DFT calculations, a plausible reaction mechanism involved synergistic dual activation catalysis of [N1111][Arg] was proposed, which indicated that DMC and ISB were simultaneously activated by forming H-bonds with [N1111][Arg]. In addition to providing a green and economical strategy for preparation of PIC, this work also supplied an in-depth understanding of the structure-property-catalytic performance relationship of ILs.