Synthesis of bioderived polycarbonates with adjustable molecular weights catalyzed by phenolic-derived ionic liquids†
The synthesis of high-molecular-weight bioderived polycarbonates via green routes and regulation of molecular weight is of great significance and is highly challenging. Herein, a green sequential approach toward the synthesis of bio-derived polycarbonates with adjustable molecular weights from isosorbide and dimethyl carbonate (DMC) has been developed by employing ionic liquids (ILs) as a class of eco-friendly catalysts. The structures of IL catalysts can be designed readily to control the molecular weight of isosorbide-derived polycarbonates (PIC), which is an attractive advantage of IL catalysts instead of the conventional metal-containing catalysts. In the presence of the [Bmim][4-I-Phen] catalyst, the PIC weight-average molecular weight (Mw) can reach 50 300 g mol−1. By the combination of the experimental results and DFT calculations, an IL anion–cation synergistic catalytic polymerization mechanism has been proposed, which reveals the nucleophile–electrophile dual activation by H-bonds and charge–charge interactions in catalyzing the formation of PIC. The significance of this study is that it provides guidance for developing IL catalysts for synthesizing higher molecular weight polycarbonates, thereby conveniently leading to a variety of polymers with tunable properties.