Synthesis of biodegradable polycarbonate by alternating copolymerization of carbon dioxide and propylene oxide using a cobalt/Schiff base catalyst

A series of cobalt/Schiff base complexes, (R,R)-SalenCoIIIX [Salen = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-di-phenylethylenediimine; X = OOCCF3 (1), OOCCCl3 (2), and OOCCH3 (3)], were investigated for the alternating copolymerization of carbon dioxide with racemic propylene oxide in the presence of [PPN]Cl ([PPN] = bis(triphenylphosphine)iminium). The effect of the axial group X of the complexes and the reaction conditions on the yield, the selectivity for poly(propylene carbonate) over propylene carbonate, and the polymer molecular weight for this transformation were investigated. A high molecular weight of 72.5 kg mol−1 (Mn/Mw = 1.27, yield 76%) for the copolymer was achieved.