Copolymerization of epoxides and carbon dioxide by using double metal cyanide complex (DMC) with high crystallinity

Zn₃ [Co(CN)₆]₂ based double metal cyanide complex(Co-Zn DMC) is synthesized and characterized by element analysis, FT-IR, TG-FTIR, XRD and TEM. The composition of Co-Zn DMC summarized by elemental analysis has been confirmed by TG-FTIR. The catalyst has high crystallinity according to strong crystalline peaks shown in XRD and diffraction spot observed by TEM. Copolymerization of epoxides and carbon dioxide are successfully catalyzed by Co-Zn DMC. The efficiency of catalysts is as high as 7488 g polymer/g catalyst for CO₂/propylene oxide (PO), 1100 g polymer/g catalyst for CO₂/ethylene oxide (EO), which are higher than that reported ever before. The effects of various reaction conditions such as amount of the catalyst, reaction time and temperature on the copolymerization are investigated. The results show that insertion of CO₂ into chains is significantly affected by the catalyst quantity and ambient temperature. The weight percentage of byproduct cyclic carbonate can be easily controlled to be less than 5% while the molar fraction of CO₂ in backbone (f_co2) is more than 30%.