Performance tailorable terpolymers synthesized from carbon dioxide, phthalic anhydride and propylene oxide using Lewis acid-base dual catalysts

Abstract

Bulk terpolymerization of carbon dioxide and phthalic anhydride with propylene oxide is successfully carried out using metal-free and economical Lewis pairs under mild conditions. A series of commercial organic bases are coupled with triethyl borane (TEB) as Lewis pairs to optimize the activity and the results show that the TEB/ bis(triphenylphosphine)iminium chloride (PPNCl) pair exhibits relatively high activity and selectivity. The impact of the molar ratio of TEB to organic bases, reaction temperature and CO2 pressure as well as the catalyst loading on the activity and selectivity of the copolymerization are investigated. Particularly, the turnover frequency reaches 164 h−1 with a TEB/PPNCl molar ratio of 2/1 at 80 °C. To our delight, the poly(ester-co-carbonate)s with random or block structures can be simply tuned by choosing different organic bases coupled with TEB. In these cases, the resultant terpolymers with comprehensive properties can be readily synthesized. As expected, the incorporation of phthalic anhydride effectively modifies the thermal and mechanical properties of commercial poly(propylene carbonate) (PPC). Terpolymers named as PPC-P with 43 mol% aromatic polyester moieties displays a glass transition temperature (Tg) of 47 °C, about 9 °C higher than that of commercial PPC, and gives a tensile strength higher than 37.6 MPa. To our delight, the synthesized PPC-P exhibits satisfactory degradation speed under standard composting condition compared with commercial PBAT and PPC.