A Non-phosgene Synthetic Process for Bioderived Polycarbonate with High-molecular-weight and Advanced Property Profile Catalyzed by Amino Acid Ionic Liquids

The conversion of biomass and carbon dioxide to plastics is one of the key solutions to reduce the greenhouse effect and alleviate the petroleum resource depletion. However, there is still a lack of bioderived polymers with high molecular weight, excellent performance and their corresponding green synthesis process, thus which limits the potential of bioderived polymers to replace petroleum-based polymers. In this paper, an eco-friendly synthetic process for bioderived polycarbonate catalyzed by amino acid ionic liquids was developed by utilizing isosorbide (ISO) and diphenyl carbonate (DPC) as reactants, which are derived from renewable resource and carbon dioxide, respectively. By using 1-ethyl-3-methylimidazole lysine ([Emim][Lys]) as catalyst, poly(isosorbide carbonate) (PIC) with the weight average molecular weight of 150 000, the highest so far to the best of our knowledge, was synthesized and the Tg of PIC was up to 174 oC. The reaction mechanism was investigated using nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS), density functional theory (DFT) calculation, and the remarkable catalytic performance was attributable to the fact that [Emim][Lys] can effectively activate the hydroxyl group of ISO and carbonyl group of DPC, and inhibit the formation of cyclic intermediates. Moreover, to overcome the brittleness of PIC, 1,4-butanediol (BD) and 1,4-cyclohexanedimethanol (CHDM) were introduced into PIC, and the copolycarbonate showed excellent Young’s modulus, ultimate tensile strength, and elongation at break, which were 979 MPa, 57 MPa, and 145%, respectively, which was comparable to the commercial petroleum-based polycarbonates. Such process provides a further industrial prospect for the next generation of bioderived polycarbonate.