Mono‐ and binuclear nickel catalysts for 1‐hexene polymerization

Dechal, Abbas; Khoshsefat, Mostafa; Ahmadjo, Saeid; Mortazavi, Seyed Mohammad Mahdi; Zohuri, Gholamhossein; Abedini, Hossein

doi:10.1002/aoc.4355

Cited by 24 publications

(28 citation statements)

References 73 publications

(131 reference statements)

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“…Molecular weight distributions (MWDs) were determined with a Polymer Char high-temperature gel permeation chromatography (GPC) instrument, run at 145°C under a flow of 1,2,4-trichlorobenzene at a rate of 1 ml min −1 . [51,52] The catalysts studied were mononuclear (M 1 and M 2 ) and dinuclear (C 1 -C 6 ) Ni α-diimine-based catalysts. [49] 13 C NMR spectra of polyethylene were recorded with a Bruker AC-400 MHz instrument at 115°C in deuterated tetrachloroethane with tetramethylsilane as an internal standard.…”

Section: Characterizationmentioning

confidence: 99%

“…[53] This effect also implies the steric and electronic impacts of ligand architecture and metal center. [52] This suggested that the presence of acenaphthene could make the active center to be a better π-acceptor. The effect of backbone was observed for catalysts M 2 and C 4 in comparison to M 1 and C 3 , respectively.…”

Section: Ethylene Polymerization Catalyzed By Mononuclear and Dinucmentioning

confidence: 99%

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Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Khoshsefat

Dechal

Ahmadjo

et al. 2019

Applied Organom Chemis

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A series of mononuclear (M 1 and M 2 ) and dinuclear (C 1 -C 6 ) Ni α-diimine catalysts activated by modified methylaluminoxane were used in polymerization of ethylene. Catalyst C 2 bearing the optimum bulkiness showed the highest activity (1.6 × 10 6 g PE (mol Ni) −1 h −1 ) and the lowest short-chain branching (32.5/1000 C) in comparison to the dinuclear and mononuclear analogues.Although the mononuclear catalysts M 1 and M 2 polymerized ethylene to a branched amorphous polymer, the dinuclear catalysts led to different branched semicrystalline polyethylenes. Homogeneity and heterogeneity in the microstructure of the polyethylene samples was observed. Different trends for each catalyst were assigned to syn and anti stereoisomers. In addition, thermal behavior of the samples in the successive self-nucleation and annealing technique exhibited different orders and intensities from methylene sequences and lamellae thickness in respect of each stereoisomer behavior. Higher selectivity of hexyl branches obtained by catalyst C 2 showed a cooperative effect between the centers. The results also revealed that for catalysts C 5 and C 6 , selectivity of methyl branches led to very high endotherms and crystalline sequences with melting temperatures higher than that of 100% crystalline polyethylene indicating ethylene/propylene copolymer analogues. For catalysts C 3 and C 4 , more vinyl end groups were a result of the long distance between the Ni centers. Kinetic profiles of polymerization along with a computational study of the precatalysts and catalysts demonstrated that there is a direct relation between rate constant, energy interval of catalyst and precatalyst, and interaction energy of Et···methyl cationic active center (Et···MCC or π-Comp.). Based on this, narrow energy interval (activation energy) of precatalyst and catalyst leads to fast and higher activation rate (catalyst M 2 ), and strong interaction of ethylene and catalyst leads to high monomer uptake and productivity (catalyst C 2 ). Moreover, theoretical parameters including electron affinity, Mulliken charge on Ni, chemical potential and hardness, and global electrophilicity showed optimum values for C 2 .

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Section: Characterizationmentioning

confidence: 99%

Section: Ethylene Polymerization Catalyzed By Mononuclear and Dinucmentioning

confidence: 99%

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Khoshsefat

Dechal

Ahmadjo

et al. 2019

Applied Organom Chemis

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“…[45] Herein, two dinuclear α-diimine Ni catalysts (BNC1 and BNC2) along with their mononuclear analogues (MNC1 and MNC2) were selected based on their significant catalytic behavior and polymer properties (Scheme 1). [44,[46][47][48] To clarify, based on our previous reports, BNC1 showed the highest activity among the dinuclear structures studied in homopolymerization of ethylene and α-olefins, whereas BNC2 made polyolefins at a moderate productivity. [44,47] BNC1 also produced PE with high molecular weight and high selectivity for hexyl branches, whereas BNC2 made an ethylenepropylene copolymer (with high level of methyl branches) using only ethylene as feed.…”

Section: Introductionmentioning

confidence: 87%

“…However, higher stability of dinuclear catalyst led to higher activity in comparison with its mononuclear counterpart. [46,47,56] On the other side, the lowest activity was observed in the masked method. It could be suggested that increasing of organoaluminium (TiBA) in the reaction may prevent the monomer coordination into the catalyst active centers.…”

Section: Effect Of Different Cocatalyst On the Activity Of Bnc1 Formentioning

confidence: 94%

Microstructural study on MMA/1‐hexene copolymers made by mononuclear and dinuclear α‐diimine nickel (II) catalysts

Bagherabadi

Zohuri

Ramezanian

et al. 2020

Applied Organom Chemis

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Homogenous catalytic homopolymerization and copolymerization of 1-hexene (H) with methyl methacrylate (MMA) were carried out in presence of two different types of mononuclear (MNC1 and MNC2) and dinuclear Ni-based catalysts (BNC1 and BNC2). Modified methylaluminoxane was used as cocatalyst due to good reactivity in MMA/H copolymerization. Among the structures, BNC1 showed the highest catalyst activity (6.9 × 10 4 g P. mol −1 Ni. h −1). Although M w of the copolymer made by BNC1 was higher than its mononuclear, molecular weight distribution was broader. The optimum molar ratios for mononuclear and dinuclear were obtained at [Al]/[Ni] = 1,000:1 and [Al]/[Ni] = 1,500:1, respectively. Surprisingly, introduction of MMA (up to [MMA]/[H] = 50:50 molar ratio) into the polymerization solution increased the activity of all catalysts. 1 H NMR analysis study revealed that increasing of MMA in the feed composition raised incorporation of the comonomer into the obtained copolymers. The result was consistent on the calculated reactivity ratio of monomers, using Kelen-Tudos method. In addition, BNC1 (at [MMA]/[H] = 70:30 molar ratio) demonstrated more incorporation of MMA to the main copolymer chain (95.2% mol). On the other side, study on tacticity of the PMMA sample was investigated that showed a distribution of stereoregularity in the order of atactic > > syndiotatic > isotactic (53.2 > 26.7 > 20.1). In addition, for copolymers made by BNC1, an unusual pattern was observed as lower concentration of MMA in the feed (i.e., 30%) led to high isotactic blocks of MMA. The highest branching density of the polymer, however, was obtained by BNC1 (217/1000C) and the lowest by BNC2 (80/1000C). Higher extent of the polar comonomer (MMA) in the copolymer backbone led to increasing of T g for the copolymer samples (from 74.4 to 98.9 C). The structural properties of the obtained copolymers were investigated using both Fourier transform infrared spectroscopy and Raman spectroscopies, as well.

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“…The results were mainly included highly branched ethylene‐MM copolymers with high molar mass, [24,25] depending on MM incorporation into cocatalyst type, cocatalyst/MM ratio [6,26] and catalyst structure [27] . On the other side, multinuclear late transition metal (LTM) catalysts as well as mononuclear analogues are important due to their superior catalytic properties [2,28–32] …”

Section: Introductionmentioning

confidence: 99%

Microstructural, Thermal and Electrical Properties of Methyl Methacrylate and 1‐Hexene Copolymers Made by Dinuclear Ni‐Based Catalysts

2021

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Herein, we investigate the dinuclearity effect of α‐diimine Ni‐based catalysts, N1 and N2 bearing different backbone on methyl methacrylate/1‐hexene (MM‐1H) copolymerization and characterize the copolymers microstructures using FT‐IR and NMR. The monomer reactivity ratio (r) is calculated using three different methods, a high reactivity ratio for MM (r1=9.9611), whereas a low reactivity ratio is obtained for 1H (r2=−0.0226). As determined by NMR analyses, up to 96 % of the MM incorporated into the main chain. Thermal copolymer properties are studied by DSC and TGA analyses, and the results are compared with those of Poly (methyl methacrylate) (PMMA). The higher content of MM in the copolymer backbone and the higher Tg for the copolymer samples (95.5 to 105.6 °C) were obtained. TGA shows that the degradation temperature of copolymers with higher 1H content progression reduced by about 10 % weight‐loss for N1 (327 to 240 °C) and N2 (325 to 236 °C). We are using a novel method with a low‐cost and speedy determination of polymer conductivity in both solid and liquid phases, which indicates the semi‐conductivity property of poly(MM‐1H) using corona discharges under the air atmosphere. Synthesized graphene‐poly(MM‐1H) nanocomposite shows the electrical conductivity augment from 3.45 μS of the poly(MM‐1H) to 30.42 μS for its nanocomposite.

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Mono‐ and binuclear nickel catalysts for 1‐hexene polymerization

Cited by 24 publications

References 73 publications

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Microstructural study on MMA/1‐hexene copolymers made by mononuclear and dinuclear α‐diimine nickel (II) catalysts

Microstructural, Thermal and Electrical Properties of Methyl Methacrylate and 1‐Hexene Copolymers Made by Dinuclear Ni‐Based Catalysts

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