No abstract

Aluminum salen complexes bearing appended quaternary ammonium salt substituents have been synthesized and shown to be effective catalysts for the coupling of epoxides and carbon dioxide to generate cyclic carbonates. 27 Al NMR spectra have demonstrated that these exist as both five-and six-coordinate Al(III) species in dimethylsulfoxide (DMSO) solution, whereas only a five-coordinate Al(III) species was detected in the (salen)AlCl analogue in the presence of an external onium salt. The onium salt group tethered on the salen ligand was found to play an important role in enhancing the catalytic activity. The effects of reaction variables such as temperature, time, pressure, molar ratio of epoxide to catalyst on the catalytic performance were systematically investigated. These bifunctional catalysts were found to be highly stable to moisture and oxygen, resistant to impurities, and recyclable with only minor losses in catalytic activity.

A facile strategy has been demonstrated for the selective synthesis of highly stereoregular polyesters with cis-2,3-(exo, exo) or trans-2,3-(exo, endo) repeating units by the organocatalysts mediated alternating copolymerization of cyclohexene oxide and norbornene anhydride (NA) stereoisomers. The geometrical structure of polyester can be tuned simply by modulating the type of NA isomers (endo- or exo-NA), monomer feed ratio, and reaction temperature. The cis- (>99%) and trans-polyesters (>99%) exhibit high glass transition temperature up to 129.8 and 115.9 °C, respectively. The resulting polyesters provide a versatile platform to incorporate various functional groups through the robust thiol–ene reaction of the pendant norbornenyl groups.

So far, ligand steric effects of the α-diimine nickel catalysts on the polyolefin branching densities are not systematically investigated. Generally, in contrast to the α-diimine palladium systems, the branching densities of the polyethylene obtained by the α-diimine nickel catalysts increased when the more sterically encumbering substituent was employed. In this contribution, we described the synthesis and characterization of a series of α-diimine ligands and the corresponding nickel catalysts bearing the diarylmethyl moiety and varied steric ligands. In ethylene polymerization, the catalytic activities [(2.82–15.68) × 106 g/(mol Ni·h)], polymer molecular weights [M n: (0.37–131.51) × 104 g mol–1], branching densities [(28–81)/1000 C], and polymer melting temperatures (−4.7–122.9 °C) can be tuned over a very wide range. To our surprise, the polymer branching density first rose and then fell when we systematically increased the steric bulk of α-diimine nickel catalysts, like a downward parabola, not in line with previous conclusions. In ethylene-methyl 10-undecenoate (E-UA) copolymerization, the catalytic activities [(1.0 × 103) – (104.8 × 104) g/(mol Ni·h)], copolymer molecular weights [(1.2 × 103) – (242.4 × 103) g mol–1], branching densities [(42–70)/1000 C], and UA incorporation ratio (0.17–2.12%) can also be controlled over a very wide range. The tuning in steric ligands enables the tuning of the polymer microstructures such as molecular weight and branching density. In this way, the best polyethylene elastomer catalysts are screened out.

Poly(ethylene oxide)-based solid-state electrolytes are widely considered promising candidates for the next generation of lithium and sodium metal batteries. However, several challenges, including low oxidation resistance and low cation transference number, hinder poly(ethylene oxide)-based electrolytes for broad applications. To circumvent these issues, here, we propose the design, synthesis and application of a fluoropolymer, i.e., poly(2,2,2-trifluoroethyl methacrylate). This polymer, when introduced into a poly(ethylene oxide)-based solid electrolyte, improves the electrochemical window stability and transference number. Via multiple physicochemical and theoretical characterizations, we identify the presence of tailored supramolecular bonds and peculiar morphological structures as the main factors responsible for the improved electrochemical performances. The polymeric solid electrolyte is also investigated in full lithium and sodium metal lab-scale cells. Interestingly, when tested in a single-layer pouch cell configuration in combination with a Li metal negative electrode and a LiMn0.6Fe0.4PO4-based positive electrode, the polymeric solid-state electrolyte enables 200 cycles at 42 mA·g−1 and 70 °C with a stable discharge capacity of approximately 2.5 mAh when an external pressure of 0.28 MPa is applied.