Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Adamu, Sagir; Atiqullah, Muhammad; Malaibari, Zuhair; Al‐Harthi, Mamdouh A.; Emwas, Abdul‐Hamid; Ul‐Hamid, Anwar

doi:10.1016/j.jtice.2015.10.031

Cited by 4 publications

(4 citation statements)

References 77 publications

(94 reference statements)

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“…Such complexes are intermediates of the chain release via Zr-Al transfer [86][87][88]. At the same time, the practice of using high Al MAO /Zr ratios in the laboratory was due to lthe ow effectiveness of MAO as an alkylation agent; the Al MAO /Zr ratios of 10 2 MAO were found to be insufficient for the activation of bis-indenyl and bis-fluorenyl complexes [89]. In 2017, Nifant'ev et al proposed a two-stage activation method for a wide array of LZrCl 2 complexes.…”

Section: Metallocene-catalyzed Oligomerization Of -Olefins and Activamentioning

confidence: 99%

Fair Look at Coordination Oligomerization of Higher α-Olefins

Nifant’ev

Ivchenko

2020

Polymers

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Coordination catalysis is a highly efficient alternative to more traditional acid catalysis in the oligomerization of α-olefins. The distinct advantage of transition metal-based catalysts is the structural homogeneity of the oligomers. Given the great diversity of the catalysts and option of varying the reaction conditions, a wide spectrum of processes can be implemented. In recent years, both methylenealkanes (vinylidene dimers of α-olefins) and structurally uniform oligomers with the desired degrees of polymerization have become available for later use in the synthesis of amphiphilic organic compounds and polymers, high-quality oils or lubricants, and other prospective materials. In the present review, we discussed the selective dimerization and oligomerization of α-olefins, catalyzed by metallocene and post-metallocene complexes, and explored the prospects for the further applications of the coordination α-olefin dimers and oligomers.

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Section: Metallocene-catalyzed Oligomerization Of -Olefins and Activamentioning

confidence: 99%

Fair Look at Coordination Oligomerization of Higher α-Olefins

Nifant’ev

Ivchenko

2020

Polymers

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“…The melting temperatures ( T m ) at each point can thus be related to the equivalent dimensions of that crystal lamella (crystallite) by using Flory and GT equations, also termed as MGT equation, given by Equation

T_{m} = T_{m}^{o} true(1 - \frac{2 σ_{s s f e}}{Δ H_{f}^{o} L_{f c l a m e l l a}} true)

where

T_{m}^{o}

(equilibrium melting temperature of perfect crystal of ethylene homopolymer) = 418.65 K;

{Δ H}_{f}^{o}

(heat of fusion per unit volume for the perfect crystal) = 290 J cm −3 ; L fclamella is the folded crystal lamellar thickness, and σ ssfe (crystallite specific surface free energy) = 90 mJ · m −2 . However, for the

T_{m}^{o}

for the copolymer (

T_{m, c o p o l y m}^{o}

) Equation is used .…”

Section: Resultsmentioning

confidence: 99%

“…It was found that the lamellar thickness of the homopolymer is much more widely distributed than the copolymers; with a high weight average lamellar thickness (WALT) calculated using Flory and GT equations. This could be ascribed to the resulting decrease in longer lamellae by the butyl branching of the copolymer …”

Section: Introductionmentioning

confidence: 99%

Crystallization behaviour and lamellar thickness distribution of metallocene‐catalyzed polymer: Effect of 1‐alkene comonomer and branch length

2016

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The effect of comonomer and branching on the melt crystallization and lamellar thickness distribution was studied for ethylene and 1‐alkene copolymers. The comonomers used in this study are 1‐hexene, 1‐octene, and 1‐decene. A notable influence of the comonomer ratio in the feed was observed on the crystallization and melting behaviour. The Ozawa and Mo models were found suitable for these copolymers. However, variation of relative crystallinity at different heating rates preferred the Mo method over the Ozawa method. The melting behaviour and lamellar thickness distribution of the copolymers were analyzed by the help of the modified Gibbs‐ Thomson equation. The activation energies (EA) for the melt crystallization were calculated using the Kissinger method. It was observed that 1‐hexene comonomer exhibits lower EA, indicating an easier crystallization process as compared to other comonomers used. Overall, crystallization was found to be more influenced by the degree of branching rather than the comonomer type.

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“…Nowadays, NMR spectroscopy is one of the most important analytical tools that has been used in several fields. These fields include structural biology [29][30][31][32][33][34][35][36][37][38], organic chemistry [39][40][41][42][43][44][45][46][47][48][49][50][51][52], polymer characterization [40,46,[53][54][55][56][57][58][59][60][61][62][63][64], inorganic chemistry [65][66][67][68][69][70][71][72][73][74][75], and physics [76][77][...…”

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confidence: 99%

New Advances in Fast Methods of 2D NMR Experiments

Emwas¹,

Alghrably²,

Al-Harthi³

et al. 2020

Nuclear Magnetic Resonance

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Although nuclear magnetic resonance spectroscopy is a potent analytical tool for identification, quantification, and structural elucidation, it suffers from inherently low sensitivity limitations. This chapter focuses on recently reported methods that enable quick acquisition of NMR spectra, as well as new methods of faster, efficient, and informative two-dimensional (2D) NMR methods. Fast and efficient data acquisition has risen in response to an increasing need to investigate chemical and biological processes in real time. Several new techniques have been successfully introduced. One example of this is band-selective optimized-flip-angle shorttransient (SOFAST) NMR, which has opened the door to studying the kinetics of biological processes such as the phosphorylation of proteins. The fast recording of NMR spectra allows researchers to investigate time sensitive molecules that have limited stability under experimental conditions. The increasing awareness that molecular structures are dynamic, rather than static, has pushed some researchers to find alternatives to standard, time-consuming methods of 15 N relaxation observables acquisition.Keywords: NMR, 2D NMR, ultrafast data processing, SOFAST, relaxation 15 N, 29 Si, 30 Al, 31 P to 235 U). As the resonating frequency is unique for each type of nuclei, one can envision an NMR for each nucleus as a separate spectroscopy such as 1 H NMR spectroscopy, 13 C NMR spectroscopy, 235 U NMR spectroscopy (Figure 1), etc. More importantly, NMR has the ability to evaluate information about the environment of each atom and their neighbor's nuclei (both through space and through bond), allowing researchers to differentiate the unique magnetic environments of the same nuclei in different positions of a single molecule. Thus, NMR spectroscopy is extensively used for the identification and in the structural elucidation in a wide Nuclear Magnetic Resonance 2 range of applications in gas [2,3], liquid [4][5][6][7][8][9][10][11][12][13][14][15][16], and solid-state samples [17][18][19][20][21][22][23][24][25][26][27][28]. Nowadays, NMR spectroscopy is one of the most important analytical tools that has been used in several fields. These fields include structural biology [29][30][31][32][33][34][35][36][37][38], organic chemistry [39][40][41][42][43][44][45][46][47][48][49][50][51][52], polymer characterization [40,46,[53][54][55][56][57][58][59][60][61][62][63][64], inorganic chemistry [65][66][67][68][69][70][71][72][73][74][75], and physics [76][77][78][79][80][81][82][83].Despite its significant advantages, NMR suffers from some limitations, of which the relatively low sensitivity seems to be the most severe. An NMR sample can be treated as a collection of many nuclear spins of magnetically active nuclei that act as small bar magnets. These nuclear spins have two possible orientations with different energy levels that adapt when placed within the strong magnetic field. The number of nuclear spins occupying each energy level is determined by the Boltzmann distribution equation: N ...

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Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Cited by 4 publications

References 77 publications

Fair Look at Coordination Oligomerization of Higher α-Olefins

Fair Look at Coordination Oligomerization of Higher α-Olefins

Crystallization behaviour and lamellar thickness distribution of metallocene‐catalyzed polymer: Effect of 1‐alkene comonomer and branch length

New Advances in Fast Methods of 2D NMR Experiments

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