Low-molecular weight oligo(carbonate-ether) diols are important raw materials for polyurethane formation, which with tunable carbonate unit content (CU) may endow new thermal and mechanical performances to polyurethane. Herein, facile synthesis of oligo(carbonate-ether) diols with number average molecular weight (Mn) below 2000 g mol-1 and CU tunable between 40% and 75% are realized in high activity by immortal copolymerization of CO2/propylene oxide (PO) using zinc-cobalt double metal cyanide complex (Zn-Co-DMCC) in the presence of sebacic acid (SA). Mn of the oligomer is in good linear relationship to the mole ratio of PO and SA (PO/SA) and hence can be precisely controlled by adjusting PO/SA. Besides, the molecular weight distribution is quite narrow due to the rapid reversible chain transfer in the immortal copolymerization. High pressure and low temperature are favorable for raising CU. In all the reactions, the weight fraction of propylene carbonate (WPC) can even be controlled as low as 2.0 wt %, and the catalytic activity of Zn-Co-DMCC is above 1.0 kgg-1 cat. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012