Organonitriles as complexing agents for the double metal cyanide-catalyzed synthesis of polyether, polyester, and polycarbonate polyols

A series of double metal cyanide (DMC) catalysts prepared using nitrile compounds as complexing agents (CAs) was employed for the synthesis of polyether, polyester, and polycarbonate polyols. The DMC catalysts bearing nitrile CAs exhibited remarkably higher activities toward the ring-opening polymerization (ROP) of propylene oxide (PO) and ε-caprolactone (CL), as well as toward the copolymerization of PO with CO2, than conventional DMC catalysts prepared using tert-butyl alcohol as a CA. Accordingly, DMC catalysts bearing 2-methylbutyronitrile or isobutyronitrile showed the highest activities for the ROP of PO (TOF = 533 min−1) and CL (TOF = 83 h−1), respectively, whereas the DMC using acetonitrile CA exhibited the highest efficiency for the copolymerization of PO and CO2 (TOF = 475 h−1). The resultant polypropylene oxide polyols were characterized by a narrow polydispersity index (1.1 −1.2) and a low unsaturation level (0.004−0.014). In addition, the DMC catalyst bearing isobutyronitrile afforded α,ω-hydroxyl-terminated polycaprolactones with controlled molecular weights (1000−9800 g mol−1) and a narrow polydispersity index of 1.1−1.5. Polycarbonate polyols with relatively high yields (56–67 %) and carbonate contents (30–38 %) were also obtained.