Synthesis of novel double metal cyanide catalysts and polymerization of PO and CO2

Double metal cyanides (DMC) are a versatile group of complexes that find numerous applications in catalytic conversions, e.g. as catalysts for polycondensation of diols and diacids[1], for the ring-opening polymerization of epoxides[2] and their co- and terpolymerization with CO2[3] and cyclic anhydrides.[4] The DMC catalysts usually have a high selectivity; in case of propylene oxide ring opening polymerizations (and in contrast to e.g. alkali-based catalysts), products with low degrees of unsaturation and narrow molecular weight distributions are obtained. A major challenge in the application of DMC catalysts is that they generally feature an induction period of several minutes up to hours during which no substantial propagation is observed. The length of the induction period is affected for instance by the catalyst preparation itself but also by the presence of impurities.[6,7] Up to this date, no reliable model exists that allows the prediction of the length of this activation step. This does not only result in decreasing overall space-time yield but also is a serious safety issue as the spontaneous initiation at the end of the induction period causes an increase in temperature due to the exothermic polymerization reactions. Please click Additional Files below to see the full abstract