Synthesis of Bioderived Polycarbonates with Molecular Weight Adjustability Catalyzed by Phenolic-derived Ionic Liquids
Synthesis of high-molecular-weight bioderived polycarbonates via green routes and regulation of molecular weight are of great significance but also enormous challenges. Herein, a green sequential approach toward the bio-derived polycarbonates with adjustable molecular weight from isosorbide and dimethyl carbonate (DMC) has been developed by employing ionic liquids (ILs) as a class of eco-friendly catalyst. The structures of IL catalysts are capable of being designed readily to control the molecular weight of isosorbide-derived polycarbonate (PIC), which is an attractive advantage of IL catalysts instead of the conventional metal-containing catalysts. In the presence of [Bmim][4-I-Phen] catalyst, PIC weight-average molecular weight (Mw) can reach to 50300 g/mol. By combination of the experimental results and DFT calculations, an IL’s anion-cation synergistic catalytic polymerization mechanism has been proposed, which reveals that nucleophile electrophile dual activation by H-bonds and charge-charge interactions in catalyzing PIC formation. Further importance of this study is that we propose a guidance of developing IL catalysts for synthesizing higher molecular weight polycarbonates, thereby conveniently preparing a variety of polymers with tunable properties.