Synthesis of Disentangled Ultra‐High Molecular Weight Polyethylene using Vanadium(V)‐Based Catalysts

Spronck, Mitch; Klein, Axel; Blom, Burgert; Romano, Dario

doi:10.1002/zaac.201800165

Cited by 21 publications

(17 citation statements)

References 39 publications

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“…Compounds 6 and 7 were prepared from the vanadium(V) trichloride complex 16 as summarized in Scheme , following well-established procedures . The molecular structures determined by single crystal X-ray diffraction are depicted in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…29 If, however, bimolecular decomposition occurred, higher conversions would be expected for 6 and 7, given the increased steric bulk. Compounds 6 and 7 were prepared from the vanadium(V) trichloride complex 16 72 as summarized in Scheme 6, following well-established procedures. 27 The molecular structures determined by single crystal X-ray diffraction are depicted in 27 The syn isomer for the alkylidene is observed in the solid state structure, and is the dominant species in solution (95% by 1 H NMR).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Celite was oven-dried for several days before use in the glovebox. Compounds 1 , 5 , and 16 were prepared as described in the literature. All other reagents were used as received.…”

Section: Experimental Sectionmentioning

confidence: 99%

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Decomposition of Vanadium(V) Alkylidenes Relevant to Olefin Metathesis

et al. 2020

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Vanadium alkylidenes can be highly active initiators for ring-opening metathesis polymerization of cyclic olefins; however, attempts to expand their use to cross metathesis have been unsuccessful due to catalyst decomposition. Detailed knowledge of the decomposition reaction is imperative to guide future catalyst design. Herein, we demonstrate that β-hydride elimination is the dominant decomposition pathway during cross metathesis. The isolated vanadium decomposition products 11), generated from two separate catalysts, agree with this pathway. Compounds 10 and 11 were shown computationally to form via bimolecular routes after β-hydride elimination from the metallocyclobutane and reductive elimination of propylene, which was itself demonstrated to be exergonic with low thermodynamic barriers to metallocyclobutane formation. Relative conversions in the selfmetathesis of 1-hexene with the series of vanadium alkylidenes of various sterics and electronics ( 6), X = CH(CH 3 ) 2 , Y = F (7)] were determined. It was found that bulkier, yet more electron-donating ligands decreased conversions, indicating that β-hydride elimination is favored over bimolecular decomposition. Analysis of organic reaction products demonstrated that reductive elimination of propylene occurs before insertion of ethylene into the newly formed vanadium−hydrogen bond.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

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Decomposition of Vanadium(V) Alkylidenes Relevant to Olefin Metathesis

et al. 2020

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“…The initial values of the normalized modulus, G t ′ / G max ′ , where G max ′ was taken from the modulus at t = 3 h, fell in the range of 0.57–0.62 (Figure S3a), indicating the weakly entangled state of nascent powder. Note that the values of the normalized modulus ( G t ′ / G N 0 ) between 0.35 and 0.7 were observed for dis- or less entangled UHMWPE produced from single-site catalysts. , In fact, the actual initial values must be smaller than the values reported here due to G max ′ < G N 0 . From the time sweep results, the effect of the chlorination time on the initial entanglement state is less clear.…”

Section: Results and Discussionmentioning

confidence: 47%

“…Since most of the entanglements are created at an early stage of polymerization, , dis- or less entangled UHMWPE can be directly obtained from polymerization under a condition that a single polymer chain crystallizes as soon as it comes out without overlapping with the others. Various homogeneous catalyst systems have been successfully used for producing dis- or less entangled UHMWPE, ,− where the spatial distance between the growing chains can be controlled by an active-site dilution. Besides, polymerization at a low temperature cooperatively helps to accelerate the crystallization of a single chain into an individual crystal.…”

Section: Introductionmentioning

confidence: 99%

Less Entangled Ultrahigh-Molecular-Weight Polyethylene Produced by Nano-Dispersed Ziegler–Natta Catalyst

Chammingkwan

Bando

Tuyet

et al. 2021

Ind. Eng. Chem. Res.

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In this study, a new strategy to produce less entangled ultrahigh-molecular-weight polyethylene (UHMWPE) was proposed based on the exploitation of a nano-dispersed MgO/MgCl2/TiCl4 core–shell catalyst. Due to its poreless nature and the full dispersion of a single primary particle, the polymer chains grown from the catalyst surface can immediately crystallize without the disturbance of other polymer chains confined in pores. The melting characteristics of annealed polymer, the rheological properties, and the solid-state drawability of synthesized polymer clarified that the nano-dispersed catalysts enabled the production of less entangled UHMWPE even under an industrial condition. Featured with a tunable active-site density through the control of chlorination and the selection of a co-catalyst, more weakly entangled UHMWPE can be obtained at a reasonable activity.

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Access to Disentangled Ultrahigh Molecular Weight Polyethylene via a Binuclear Synergic Effect

et al. 2022

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Disentangled ultrahigh molecular weight polyethylene (dis-UHMWPE) has excellent processability but can be achieved under extreme conditions. Herein, we report ethylene polymerization with the binuclear half-sandwich scandium complexes C1-Sc 2 and C2-Sc 2 to afford UHMWPE. C1-Sc 2 bearing a short linker shows higher activity and gives higher molecular weight PEs than C2-Sc 2 containing a flexible spacer and the mononuclear Sc 1 . Strikingly, all UHMWPEs isolated from C1-Sc 2 under broad temperature range (25-120 °C) and wide ethylene pressures (2-13 bar) feature very low degree of entanglement as proved by rheological test, DSC annealing study and SEM. These dis-UHMWPEs are facilely mediated solid-state-process at 130 °C and their tensile strength and modulus reach up to 149.2 MPa and 1.5 GPa, respectively. DFT simulations reveal that the formation of dis-UHMWPE is attributed to the binuclear synergic effect and the agostic interaction between the active center and the growing chain.

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Synthesis of Disentangled Ultra‐High Molecular Weight Polyethylene using Vanadium(V)‐Based Catalysts

Cited by 21 publications

References 39 publications

Decomposition of Vanadium(V) Alkylidenes Relevant to Olefin Metathesis

Decomposition of Vanadium(V) Alkylidenes Relevant to Olefin Metathesis

Less Entangled Ultrahigh-Molecular-Weight Polyethylene Produced by Nano-Dispersed Ziegler–Natta Catalyst

Access to Disentangled Ultrahigh Molecular Weight Polyethylene via a Binuclear Synergic Effect

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