High-Activity, Single-Site Catalysts for the Alternating Copolymerization of CO₂ and Propylene Oxide

Abstract

Despite recent advances regarding catalysts for CO2/epoxide copolymerization, the development of high-activity catalysts for alternating polymerization of CO2 and commodity epoxides, such as propylene oxide, remains a challenge. A new class of unsymmetrically substituted beta-diiminate zinc complexes is reported that exhibits unprecedented activity for CO2/propylene oxide copolymerization. The polymers formed are of high molecular weight (Mn approximately 35 kg/mol) and have narrow polydispersities (PDI approximately 1.1), consistent with a living polymerization.

Green Polymer Chemistry and Bio‐based Plastics: Dreams and Reality

“…[ 52 ] Since the early advances during the 1960s, several highly active catalyst generations have been developed for alternating copolymerization of propylene oxide with carbon dioxide to produce high-molecular-weight polypropylene carbonates. [53][54][55] As expected for amorphous polymers with glass transition temperatures slightly above room temperature, most amorphous polypropylene carbonates are rather soft materials and are of interest as blend components with a low carbon footprint. Dihydroxy-terminated polypropylene carbonates are of special interest as a substitute for conventional polyester polyols in polyurethane synthesis.…”

Alternating copolymerization of CO2 with propylene oxide and terpolymerization with aliphatic epoxides by bifunctional cobalt Salen complex

“…After the pioneering work by Inoue and co-workers 5,6 in the late 1960s, a wide variety of metal catalysts were developed for this transformation. [7][8][9][10][11][12][13][14][15][16][17][18] Among the metal complex catalysts, Co Schiff base complexes are effective catalysts for CO 2 / epoxides coupling reactions, 11,13,[15][16][17] because these complexes can control the molecular weights and distribution of the polycarbonates produced and regulate the selective formation of alternating copolymers. However, Co Schiff base complexes are not highly active at a high monomer/catalyst mole ratio in conjunction with a Lewis base or organic salt, which prevents them from becoming commercially viable.…”

Chemoselective Alternating Copolymerization of Limonene Dioxide and Carbon Dioxide: A New Highly Functional Aliphatic Epoxy Polycarbonate

“…The BDI zinc complex employed in our study has been reported to be inactive in the PO/CO 2 reaction for producing PPC or propylene carbonate. [13] Therefore, a preferred reactivity of (Et-BDI)Zn[N(SiMe 3 ) 2 ] towards the 1,2-epoxide group of LDO is expected due to the even bulkier substituents in the 8,9-epoxide moiety compared with PO. The 1 H NMR spectra of the PLOCs from Table 1 revealed low intensity signals in the cyclic carbonate methylene region (d = 4.0 and 4.2 ppm).…”

“…[7c, 13] However, the copolymerization of vinyl cyclohexene dioxide (VCHDO), which bears a mono-substituted oxirane similar to PO, catalyzed by the same Zn species led to gelation (Entry 10 in Table 1). Soluble aliphatic polycarbonates with a tunable number of cyclic carbonate and epoxide pendent groups have been synthesized through (ONSO)CrCl-mediated VCHDO/CO 2 copolymerizations.…”