Short-Chain Branched Polar-Functionalized Linear Polyethylene via “Tandem Catalysis”

A Novel Strategy to Directly Quantify Polyethylene Microplastics in PM2.5 Based on Pyrolysis-Gas Chromatography-Tandem Mass Spectrometry

The broad application of plastic products has resulted in a considerable release of microplastics (MPs) into the ecosystem. While MPs in other environmental matrices (e.g., soil and water) have been studied for a long time, the atmospheric fine particulate matter (PM_2.5)-bound MPs are rarely investigated due to the lack of an appropriate analytical approach. The prevalently used visual and spectroscopic means (e.g., optical microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy) suffer from obvious drawbacks that cannot precisely detect MPs of tiny sizes and provide quantitative information. In the present study, a novel strategy that does not require sample pretreatment was developed to first effectuate accurate quantification of polyethylene MP (PE-MP) in PM_2.5 based on pyrolysis-gas chromatography-tandem mass spectrometry (Pyr-GC-MS/MS). It featured acceptable recoveries (97%-110%), high sensitivity (LOD = 1 pg), and qualified precisions (RSD of 3%-13%). Employing this approach, for the first time, exact atmospheric concentrations of PE-MPs in PM_2.5 from megacities in North (Zhengzhou and Taiyuan) and South (Guangzhou) China were obtained, and relatively serious pollution was found in Taiyuan. The 100% sample detection rates also suggested the widespread occurrence and possible human exposure risks of PM_2.5-bound PE-MPs. In brief, the new strategy could conduct direct, sensitive, and accurate quantification of PE-MP in PM_2.5, favoring further studies of environmental fates, distributions, and toxicities of atmospheric MPs.

Multicatalytic Transformation of (Meth)acrylic Acids: a One-Pot Approach to Biobased Poly(meth)acrylates

Shifting from petrochemical feedstocks to renewable resources can address some of the environmental issues associated with petrochemical extraction and make plastics production sustainable. Therefore, there is a growing interest in selective methods for transforming abundant renewable feedstocks into monomers suitable for polymer production. Reported herein are one-pot catalytic systems, that are active, productive, and selective under mild conditions for the synthesis of copolymers from renewable materials. Each system allows for anhydride formation, alcohol acylation and/or acid esterification, as well as polymerization of the formed (meth)acrylates, providing direct access to a new library of unique poly(meth)acrylates.

Synthesis and coordination of a hybrid phosphinoferrocene sulfonamide ligand

A hybrid, phosphinoferrocene sulfonamide ligand was synthesised and studied as a ligand in Pd(ii) complexes, which were structurally characterised. Selected compounds were studied by cyclic voltammetry.

Copolymerization of Propylene with Higher α-Olefins by a Pyridylamidohafnium Catalyst: An Effective Approach to Polypropylene-Based Elastomer

In this contribution, we explored the copolymerization of propylene with higher α-olefins, including 1-octene (C8) 1-dodecene (C12), 1-hexadecene (C16) and 1-eicosene (C20), by using a dimethyl pyridylamidohafnium catalyst. A series of copolymers with varied comonomer incorporation, high molecular weight and narrow molecular weight distribution were obtained at mild conditions. The effects of the insertion of the comonomers on the microstructure, thermal and final mechanical properties were systemically studied by 13C NMR, wide-angle X-ray scattering, DSC and tensile test. Excellent mechanical performances were achieved by tuning the incorporation and chain length of the higher α-olefins. When the comonomer content reached above 12 mol.%, polypropylene-based elastomers were obtained with high ductility. A combination of excellent elastic recovery and flexibility was achieved for the P/C16 copolymers with about 20 mol.% monomer incorporation. The monomer incorporation and side chain length played a crucial role in determining the mechanical property of the outstanding polypropylene-based elastomers.

Facile functionalization of isotactic polypropylene via click chemistry

Alkynyl functionalized iPP, with 1–4 mol% comonomer incorporation, can be efficiently synthesized and conveniently converted into various functional iPPs and graft copolymers via alkynyl/N₃ reaction.

Preparation and in situ chain-end-functionalization of branched ethylene oligomers by monosubstituted α-diimine nickel catalysts

Chain-end-functionalization of (highly) branched ethylene oligomers was achieved in situ with the most/least bulky α-diimine nickel catalysts for the first time.

Methylene-Bridged Bisphosphine Monoxide Ligands for Palladium-Catalyzed Copolymerization of Ethylene and Polar Monomers

A series of palladium complexes bearing a bisphosphine monoxide with a methylene linker, that is, [κ²-P,O-(R¹₂P)CH₂P(O)R²₂]PdMe(2,6-lutidine)][BAr^F₄] (Pd/BPMO), were synthesized and evaluated as catalysts for the homopolymerization of ethylene and the copolymerization of ethylene and polar monomers. X-ray crystallographic analyses revealed that these Pd/BPMO complexes exhibit significantly narrower bite angles and longer Pd-O bonds than Pd/BPMO complexes bearing a phenylene linker, while maintaining almost constant Pd-P bond lengths. Among the complexes synthesized, menthyl-substituted complex 3f (R¹ = (1R,2S,5R)-2-isopropyl-5-methylcyclohexan-1-yl; R² = Me) showed the best catalytic performance in the homo- and copolymerization in terms of molecular weight and polymerization activity. Meanwhile, complex 3e (R¹ = t-Bu; R² = Me) exhibited a markedly higher incorporation of comonomers in the copolymerization of ethylene and allyl acetate (≤12.0 mol %) or methyl methacrylate (≤0.6 mol %). The catalytic system represents one of the first examples of late-transition-metal complexes bearing an alkylene-bridged bidentate ligand that afford high-molecular-weight copolymers from the copolymerization of ethylene and polar monomers.

Manipulation of polymer branching density in phosphine-sulfonate palladium and nickel catalyzed ethylene polymerization

A series of palladium and nickel catalysts bearing heteroaryl-aryl moieties were prepared and applied to ethylene polymerization and copolymerization reactions.

Copolymerisation of ethylene with polar monomers by using palladium catalysts bearing an N-heterocyclic carbene–phosphine oxide bidentate ligand

We report the synthesis and characterisation of palladium complexes bearing an N-heterocyclic carbene–phosphine oxide bidentate ligand and their use as catalysts for ethylene polymerisation and ethylene/polar monomer copolymerisation.