Preparation of dual active site ionic liquids and their application in the catalytic synthesis of poly(isosorbide carbonates)

Six dual active site ionic liquid catalysts were prepared by using triethylenediamine-grafted 1-bromotetradecane as a cation and coordinating with different organic anions. The structures and properties of the catalysts were characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA). The synthesis of poly(isosorbide carbonates) (PICs) via the transesterification polycondensation of dimethyl carbonate (DMC) and isosorbide (ISB) catalyzed by a cation and anion was studied. A single factor experiment was used to investigate optimal process parameters. FT-IR, NMR, TGA, and differential scanning calorimetry (DSC) were adopted to characterize the structures and properties of PICs. The results showed that under the same process parameters, the catalyst using imidazole as an anion had the best catalytic performance. Under optimal process conditions, the conversion of ISB reached 98.82%, the weight average molecular weight of the PIC reached 28 840 g mol-1, and the glass transition temperature (Tg) of the PIC was 149 degrees C. The present study demonstrates a process for the catalytic synthesis of bio-based polycarbonates using an ionic liquid catalyst.