Carbon Dioxide/Epoxide Copolymerization via a Nanosized Zinc–Cobalt(III) Double Metal Cyanide Complex: Substituent Effects of Epoxides on Polycarbonate Selectivity, Regioselectivity and Glass Transition Temperatures

Abstract

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.

Stereochemical enhancement of polymer properties

“…Stereopure (atactic, isotactic, and syndio-enriched) PPC is a ductile thermoplastic that has been studied for some time. [136][137][138][139][140][141] However, thermal and mechanical data on the stereopure materials is noticeably lacking, except for one study that examined the effects of regioregularity in PPC and derivatives. 136 To date, one of the most interesting epoxide-based polymers is enantiopure poly(propylene succinate).…”

“…[136][137][138][139][140][141] However, thermal and mechanical data on the stereopure materials is noticeably lacking, except for one study that examined the effects of regioregularity in PPC and derivatives. 136 To date, one of the most interesting epoxide-based polymers is enantiopure poly(propylene succinate). 142 By mixing the two enantiopure isotactic polymers that display slow crystallisation kinetics, a stereocomplex was formed with a dramatic improvement in crystallisation rate and T m .…”

Functional Polycarbonates from Carbon Dioxide and Tailored Epoxide Monomers: Degradable Materials and Their Application Potential

“…However, Zhang and co‐workers showed that also aliphatic polycarbonates with a flexible backbone may exhibit T g s up to 84 °C depending on their side chains. While the T g decreases with increasing alkyl length to −38 °C, the glass transition may increase up to 84 °C by steric influences . Also long alkyl side chains with up to 20 carbon atoms were already incorporated in aliphatic polycarbonates to tune the thermal properties .…”

DMC-Mediated Copolymerization of CO2 and PO—Mechanistic Aspects Derived from Feed and Polymer Composition

“…The immortal polymerization of PO in the presence of alcohols is a prominent feature of industrially applied double metal cyanide (DMCs) complexes for the preparation of narrow distributed polypropylene glycols [62]. The DMC catalysts for propoxylation may also yield poly(ether carbonates) when CO 2 is admitted, usually giving products with large contents of ether blocks (f carb << 75 mol%) [63][64][65] and with a lower activity [66]. The immortal copolymerization of CO 2 and epoxides can also be mediated by zinc carboxylate and DMC catalysts, giving a product with the signature of both catalysts [67].…”