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Although zinccobalt (III) double metal cyanide complex (ZnCo (III) DMCC) catalyst is a highly active and selective catalyst for carbon dioxide (CO2)/cyclohexene oxide (CHO) copolymerization, the structure of the resultant copolymer is poorly understood and the catalytic mechanism is still unclear. Combining the results of kinetic study and electrospray ionization‐mass spectrometry (ESI‐MS) spectra for CO2/CHO copolymerization catalyzed by ZnCo (III) DMCC catalyst, we disclosed that (1) the short ether units were mainly generated at the early stage of the copolymerization, and were hence in the “head” of the copolymer and (2) all resultant PCHCs presented two end hydroxyl (OH) groups. One end OH group came from the initiation of zinchydroxide (ZnOH) bond and the other end OH group was produced by the chain transfer reaction of propagating chain to H2O (or free copolymer). Adding t‐BuOH (CHO: t‐BuOH = 2:1, v/v) to the reaction system led to the production of fully alternating PCHCs and new active site of ZnOt‐Bu, which was proved by the observation of PCHCs with one end Ot‐Bu (and OCOOt‐Bu) group from ESI‐MS and 13C NMR spectra. Moreover, Zn−OH bond in ZnCo (III) DMCC catalyst was also characterized by the combined results from FT‐IR, TGA and elemental analysis. This work provided new evidences that CO2/CHO copolymerization was initiated by metalOH bond. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

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In this study, we describe the substituent effect of epoxides on CO 2 / epoxide copolymerization catalyzed by a nanosized zinc−cobalt(III) double metal cyanide complex [Zn−Co(III) DMCC]. The Zn−Co(III) DMCC catalyzed the copolymerization of CO 2 with 11 epoxides with alkyl or aryl groups at 50−60°C within 15 h. The reaction afforded various CO 2 /epoxide copolymers with high epoxide conversion efficiencies up to 100%. The alternating degree (F CO 2 ) of the resulting copolymer was solely decided by the steric hindrance of the substituents of the epoxides regardless of their electron-donating or withdrawing properties. Substituents with large steric hindrances (2, 2-dimethyl, tert-butyl, cyclohexyl, decyl, and benzyl) led to highly alternating degrees (up to 100%). The regioselective CO 2 /epoxide copolymerization was dominated by the electron induction effect of the substituent. The electron-withdrawing substituent such as phenyl and benzyl induced regioselective ring-opening at the methine site of the epoxide. For CO 2 /isobutene oxide copolymerization, the regioselective reaction occurred at the methylene site of the isobutene oxide because of the strong electron-donating ability and steric hindrance of the two methyls of the isobutene oxide. The linear alkyl groups of the epoxides could not induce the regioselective reaction during copolymerization. The glass transition temperatures (T g s) of the CO 2 /epoxide copolymers with linear alkyl substituent groups decreased from +6 to −38°C with increasing alkyl length, but increased from 6 to 84°C with increasing steric hindrance of the epoxide substituents. Thus, various CO 2 /epoxide copolymers with a wide T g range from −38 to +84°C were provided and could be applied as elastomers or plastics.

Perfectly alternating copolymerization of CO2 with a bio-based epoxide is reported with a heterogeneous Zn–Co(iii) DMCC, affording copolymers with low Tg values of −38 to −44 °C and two end hydroxyl groups.