Dual Site Alkaline Ionic Liquid-Mediated Mild Catalysis for the Synthesis of Bioderived Polycarbonate

The production of bioderived polycarbonate (PIC) via the transesterification polycondensation between dimethyl carbonate (DMC) and isosorbide (ISB) effectively mitigates the dependence on fossil resources and reduces carbon emissions. Nonetheless, the catalysts identified for this process necessitate the polymerization of bioderived polycarbonate at elevated reaction temperatures, which affected the green development of the reaction. Therefore, the design and synthesis of highly effective catalysts for the catalytic production of bioderived polycarbonate under mild conditions are of paramount importance. This study presents a modification to the structure of nitrogenous organic base dual active site ionic liquids. This structural modification enhances the activation of bimolecular reactants through the distinct involvement of both anionic and cationic sites. The conversion rate of ISB reached 97.8%, while the yield of PIC reached 95.2%. At approximately 200 °C, the viscosity-average molecular weight (Mv) of PIC was measured at 15 117 g/mol. This approach effectively optimized the transformation and polymerization of the reactants while significantly lowering the reaction temperature. The interaction energy between the anions and cations within the dual site ionic liquid could effectively modulate the activation of reactant molecules by investigating this reaction mechanism. Subsequently, FT-IR, TGA, and DSC analyses confirmed the structure and properties of PIC, revealing a bioderived polycarbonate with favorable thermal stability (Tg = 149.04 °C, Td, max = 357 °C) and sufficient molecular weight. Therefore, this catalytic system enables the environmentally benign and sustainable production of bioderived polycarbonate under mild reaction conditions.