ZnGA–MMT catalyzed the copolymerization of carbon dioxide with propylene oxide

Synthesis of Aliphatic Polycarbonates from Diphenyl Carbonate and Diols over Zinc (II) Acetylacetonate

APCs (aliphatic polycarbonates) are one of the most important types of biodegradable polymers and widely used in the fields of solid electrolyte, biological medicine and biodegradable plastics. Zinc-based catalysts have the advantages of being low cost, being non-toxic, having high activity, and having excellent environmental and biological compatibility. Zinc (II) acetylacetonate (Zn(Acac)₂) was first reported as a highly effective catalyst for the melt transesterification of biphenyl carbonate with 1,4-butanediol to synthesize poly(1,4-butylene carbonate)(PBC). It was found that the weight-average molecular weight of PBC derived from Zn(Acac)₂ could achieve 143,500 g/mol with a yield of 85.6% under suitable reaction conditions. The Lewis acidity and steric hindrance of Zn²⁺ could obviously affect the catalytic performance of Zn-based catalysts for this reaction. The main reasons for the Zn(Acac)₂ catalyst displaying a higher yield and M_w than other zinc-based catalysts should be ascribed to the presence of the interaction between acetylacetone ligand and Zn²⁺, which can provide this melt transesterification reaction with the appropriate Lewis acidity as well as the steric hindrance.

Fabrication and characterization of the ternary composite catalyst system of ZnGA/RET/DMC for the terpolymerization of CO2, propylene oxide and trimellitic anhydride

To achieve the poly(propylene carbonate trimellitic anhydride) (PPCTMA) with excellent performance, high molecular weight, enhanced yield and good thermal stability, the ternary composite catalyst system of zinc glutarate/rare earth ternary complex/double metal cyanide (ZnGA/RET/DMC) was proposed to perform the terpolymerization of CO₂, propylene oxide and trimellitic anhydride. Since the crystallinity and surface activity point of Zn–Co DMC could significantly influence the catalytic ability, mechanical ball milling was applied to increase the surface area of the Zn–Co DMC catalyst with better surface activity point. Moreover, the ZnGA/RET/DMC composite catalytic system and polycarbonate products were comparatively evaluated by XRD, SEM, FT-IR, TGA, NMR, XPS and TEM. Experimental results showed that the ZnGA/RET/DMC composite catalyst system displayed outstanding synergistic effect on the terpolymerization of CO₂, PO and TMA with better selectivity, activity, and higher molecular weight (M_w) tercopolymer than those of the individual catalyst. According to optimum reaction conditions, the M_w of PPCTMA could be up to 8.29 × 10⁴ g mol⁻¹, and the yield could be up to 66 g_polym/g_cat. The alternating tercopolymer, PPCTMA, showed wonderful thermal stability and high decomposition temperature (TGA_10% = 313 °C). A possible synergistic catalytic mechanism of the ZnGA/RET/DMC ternary composite catalyst system was also conjectured.

For poly(propylene carbonate trimellitic anhydride) with good yield, thermal stability and high molecular weight, a catalyst of zinc glutarate/rare earth ternary complex/double metal cyanide was used for terpolymerization of CO₂, propylene oxide and trimellitic anhydride.

Surface Modification of a MOF-based Catalyst with Lewis Metal Salts for Improved Catalytic Activity in the Fixation of CO2 into Polymers

The catalyst zinc glutarate (ZnGA) is widely used in the industry for the alternating copolymerization of CO2 with epoxides. However, the activity of this heterogeneous catalyst is restricted to the outer surface of its particles. Consequently, in the current study, to increase the number of active surface metal centers, ZnGA was treated with diverse metal salts to form heterogeneous, surface-modified ZnGA-Metal chloride (ZnGA-M) composite catalysts. These catalysts were found to be highly active for the copolymerization of CO2 and propylene oxide. Among the different metal salts, the catalysts treated with ZnCl2 (ZnGA-Zn) and FeCl3 (ZnGA-Fe) exhibited ~38% and ~25% increased productivities, respectively, compared to untreated ZnGA catalysts. In addition, these surface-modified catalysts are capable of producing high-molecular-weight polymers; thus, this simple and industrially viable surface modification method is beneficial from an environmental and industrial perspective.

Catalytic Chain Transfer Copolymerization of Propylene Oxide and CO2 using Zinc Glutarate Catalyst

Oligo and poly(propylene ether carbonate)-polyols with molecular weights from 0.8 to over 50 kg/mol and with 60-92 mol % carbonate linkages were synthesized by chain transfer copolymerization of carbon dioxide (CO2) and propylene oxide (PO) mediated by zinc glutarate. Online-monitoring of the polymerization revealed that the CTA controlled copolymerization has an induction time which is resulting from reversible catalyst deactivation by the CTA. Latter is neutralized after the first monomer additions. The outcome of the chain transfer reaction is a function of the carbonate content, i. e. CO2 pressure, most likely on account of differences in mobility (diffusion) of the various polymers. Melt viscosities of poly(ether carbonate)diols with a carbonate content between 60 and 92 mol % are reported as function of the molecular weight, showing that the mobility is higher when the ether content is higher. The procedure of PO/CO2 catalytic chain copolymerization allows tailoring the glass temperature and viscosity.

Synthesis of Aliphatic Carbonate Macrodiols and Their Application as Sustainable Feedstock for Polyurethane

High-molecular-weight poly(propylene carbonate) (PPC) [number-average molecular mass (M _n): 80 000-100 000] is readily alcoholized into PPC macrodiols in the presence of 1,2-propanediol (PDO), 1,4-butanediol (BDO), or 1,6-hexanediol (HDO). The high-molecular-weight PPC and small amount of diols, such as PDO, BDO, or HDO, were stirred at elevated temperatures to convert the extremely viscous high-molecular-weight polymer to low-molecular-weight macrodiols with gel permeation chromatography-measured M _n of about 3000 Da. The chopping reaction of the high-molecular-weight PPC was studied in detail, such as the influences of the catalyst residue, the kinds of alcoholysis agents, reaction temperature, and time. The reaction mechanism of alcoholysis is proposed according to the experimental results. The results indicate that the presence of a trace residue of zinc catalyst (Zn-G-III) in PPC, excess diol feeding, and higher temperature can accelerate the alcoholysis. Moreover, different diols can produce different PPC macrodiols with varying end-capping. Finally, polycarbonate ether urethane can be successfully synthesized using as-synthesized PPC macrodiols and poly(propylene glycol) (M _n ≈ 3000) as the soft segment and 4,4'-diphenylmethane diisocyanate or BDO as the hard segment. The full evaluation for the synthesized PPC macrodiols demonstrates their potential applications in the polyurethane industry.

Zinc glutarate-mediated copolymerization of CO2 and PO – parameter studies using design of experiments

Parameter studies of the PO/CO₂-copolymerization revealed the importance of the surface coverage of a nanoscopic ZnGA catalyst.

One-pot synthesis of high-molecular-weight aliphatic polycarbonates via melt transesterification of diphenyl carbonate and diols using Zn(OAc)2 as a catalyst

Aliphatic polycarbonates with M_w greater than 100 000 g mol⁻¹ with satisfactory yield can be synthesized by one-pot melt transesterification of diphenyl carbonate with aliphatic diols at equimolar amounts using Zn(OAc)₂ as a catalyst.