Double metal cyanide catalyst prepared using H3Co(CN)6for high carbonate fraction and molecular weight control in carbon dioxide/propylene oxide copolymerization

Simple mixing of H3Co(CN)6 and ZnCl2 in methanol resulted in precipitates of [ZnCl]+2[HCo(CN)6]2−, constituting a new type of double metal cyanide (DMC) catalyst exhibiting a high performance in carbon dioxide (CO2)/propylene oxide (PO) copolymerization. High-molecular-weight poly(propylene carbonate-co-propylene oxide)s [poly(PC-co-PO)s] (Mn∼40,000) were consistently obtained with high carbonate fractions (∼60 mol %) and a high selectivity (>95%) with the new type of DMC catalyst. Conventional preparation of the DMC catalyst using K3Co(CN)6 and ZnCl2 required removing KCl through thorough washing and resulted in lower carbonate fractions (10–40 mol %), which depended on the washing conditions. Feeding hydrophobic diols such as 1,10-decanediol as chain transfer agent preserved the high carbonate fraction (∼60%) and enabled precise control of the molecular weight, including preparation of a low-molecular-weight poly(PC-co-PO)-diol (Mn ∼2000), which was a flowing viscous liquid with a low Tg (−30 °C) suitable for polyurethane applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4811–4818