Synthesis of bio-based poly(oligoethylene glycols-co-isosorbide carbonate)s with high molecular weight and enhanced mechanical properties via ionic liquid catalyst

Abstract

As a kind of bio-based platform chemicals derived from renewable resource glucose, isosorbide (ISB) is considered the perfect candidate for the synthesis of polycarbonate (PC) to replace chronic toxic bisphenol A (BPA) due to its attractive rigidity, non-toxicity and chirality. However, synthesis of poly(isosorbide carbonate) (PIC) with high molecular weight and excellent mechanical properties is one of tremendous challenges due to low internal hydroxyl group activity and poor structural flexibility of ISB. Herein, we developed a new series of ISB-based copolycarbonates with intriguing properties through incorporating flexibility moiety oligoethylene glycols (OEG) into PIC. By employing bifunctional 1-butyl-3-methylimidazolium lactate IL catalyst, copolycarbonates with high weight-average molecular weight ranging from 94,700 to 146,200 were synthesized via efficient dual activation effect on the carbonyl group in diphenyl carbonate and the hydroxyl group in ISB. Among of them, poly(diethylene glycol-co-isosorbide carbonate) (PDIC) possessed excellent molecular flexibility and showed the best mechanical performance with average value of the elongation at break as high as 160%, which was eight times more than PIC prepared (18%) and much higher than the commercial BPA-based PC (around 100%). Simultaneously, PDIC showed a 1.25-fold higher tensile strength (80 MPa) than that of BPA-based PC with 63 MPa. This implied that bio-derived copolycarbonates developed in this research effectively enhanced the ductility and processability of PIC and possessed enormous prospect for the industrial application.