Double Metal Cyanide Complexes Synthesized by Solvent-Free Grinding Method for Copolymerization of CO2 and Propylene Oxide

Two active double metal cyanide (DMC) complexes were successfully synthesized by solvent-free grinding method. Their structures were characterized by FTIR spectrometer and X-ray diffractometer. The results showed that Complex 1 (double metal cyanide complex with K3Fe(CN)(6) and ZnCl2) and Complex 2 (double metal cyanide complex with K3Fe(CN)(6) and Zn(CH3COO)(2)) had the same structures, crystal forms, and lower crystallinity as both of them synthesized by conventional solvent-based methods, respectively. Investigations on grinding conditions indicated that Complex 1 ground 14 min at a high grinding strength could achieve low crystallinity and showed substantially amorphous structures. Two speculated structures of DMC were given. The alternating copolymerization of CO2 and propylene oxide with Complex 1 as catalyst obtained anticipated poly(propylene carbonate) (PPC) with very high catalytic activity. The PPC produced by optimized Complex 1 has molecular weight (M-n) up to 98,000 and narrow polydispersity of 1.93 with more than 90% carbonate linkages. Compared with Complex 1, Complex 2 displayed low catalytic activity but high selectivity mainly due to the electron atmosphere and strong steric hindrance. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 977-985, 2012