| Double metal cyanide (DMC) complexes based on Zn3[Co(CN)e]2 were prepared using different zinc salts and complexing agents and they were characterized by elemental analysis, IR and XRD. The catalytic properties of DMC complexes were determined in the ring-opening polymerization (ROP) of propylene oxide. It was found that the DMC catalyst is of nonstoichiometric nature and not air- and moisture sensitive. Great differences in morphology of DMC complexes are induced by preparation conditions. There are many factors influencing morphology of complex, such as temperature, complexing agent, addition order of starting material and the kind of zinc salts employed. The catalytic activity is strongly dependent on morphology of DMC complexes and composition of catalysts. Moreover, there is an optimum combination of preparation method and complexing agent regarding catalytic activity.It was found that substantially amorphous catalyst made from K3[Co(CN)6]2 , ZnCh and t-BuOH is of potentially high activity, which can gives polyether-polyol (Mn~8000) yields up to 48.5kg polymer/g cat. after being reformed by sulfuric salts and polyether complexing agent. In the case of such low catalyst concentration ([Co3+] <4.5 X 10~6,[Zn2+] <9.5 X 10-6) in resulting polyether polyol, separation of the catalysts is no longer required when using the polyols in polyurethane. In addition to high polymer yields, another important advantage of the DMC catalyst in this work is that it exhibited a very short induction (<10min) followed by a smooth polymerization procedure.ROP of propylene oxide catalyzed by Co-ZnDMC catalyst proceeded in acontrolled manner. Polyether polyols of moderate molecular weight (103~104) having low unsaturation (0.008~0.015meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by reacted monomer to initiator ratio (M/I). The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution (MWD)(1.18~1.39) compared with those prepared with one-step addition of monomer (MWD >2.8). Various compounds containing active hydrogen, except basic compounds and low-carbon carboxylic acid, may be used as initiators. The reaction rate increased with the increasing of catalyst amount and decreased with raising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It has also been proved that, to some extent the chain termination of this reaction system is reversible or temporary. 13C NMR analysis showed that the polymer had a head-to-tail regiosequence and a random distribution of the configurational sequences, and the end hydroxyl groups were predominantly secondary.Copolymerization of propylene oxide (PO) and ethylene oxide(EO) with mixed feed using Co-ZnDMC catalyst was carried out. The copolymer was characterized by 13C NMR/H NMR and IR spectra. The copolymer has a really random distribution of monomer unit, and the EO content in copolymer is close to that in the initial monomer feed. Moderate molecular weight copolymers with various EO content can be obtained and the values of molecular weight distribution (MWD) were in the range of 1.21~1.55. It was found that, within the limitation of molar content of EO less than 0.65, the molecular weight of copolymer is controlled by a reacted monomer(EO+PO)-to-initiator ratio. The reaction rate, as well as polymer yields decreased with increasing EO content in feed composition.Co-ZnDMC catalyst is inactive for ROP of epichlorohydrin (ECH) while it exhibits a little catalytic activity for copolymerization of ECH and PO. Polymerization rate as well as polymer yields decreased rapidly with increasing ECH content in mixed feed. Unlike copolymerization of EO and PO, the ECH content in polymer is much less than that in feed. Co-ZnDMC catalyst exhibits an excellent catalytic activity for the copolymerization of phthalic anhydride(PhA) and PO. Incontrast with copolymerization of EO and PO, or ECH and PO, the polymerization rate...
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