A ligand exchange strategy for one-pot sequential synthesis of (hyperbranched polyethylene)-b-(linear polyketone) block polymers

Zhang, Zhichao; Ye, Zhibin

doi:10.1039/c2cc33779g

Cited by 32 publications

(33 citation statements)

References 36 publications

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“…The discovery of Ni(II) and Pd(II) α‐olefin polymerization catalysts containing a bulky α‐diimine ligand, [MX 2 (α‐diimine)] (M = Ni, Pd; X = halide), by Brookhart and co‐workers, has stimulated renewed interest in the chemistry of 1,4‐diazadiene ligands and their complexes. In contrast to metallocene catalysts based on early transition metals, Ni(II) and Pd(II) catalysts produced branched polyethylene with different concentration and individual length of branches, exclusively from the ethylene monomer and accommodated even polar monomers, like acrylates .…”

Section: Introductionmentioning

confidence: 99%

New chiral α‐diimine nickel(II) complexes bearing ortho‐sec‐phenethyl groups for ethylene polymerization

Wang

Yuan

Song

et al. 2013

Applied Organom Chemis

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A series of new a-diimine nickel(II) catalysts bearing bulky chiral sec-phenethyl groups have been synthesized and characterized. The molecular structure of representative chiral ligand, bis[N,N 0 -(4-methyl-2,6-di-sec-phenethylphenyl) imino]-1,2-dimethylethane rac-1c and chiral complexes, {bis[N,N 0 -(4-methyl-2-sec-phenethylphenyl)imino]-2,3-butadiene} dibromidonickel rac-2a and bis{bis[N,N 0 -(4-methyl-2-sec-phenethylphenyl)imino]-2,3-butadiene}dibromidonickel rac-2b, were confirmed by X-ray crystallographic analysis. Complex rac-2c bearing two chiral sec-phenethyl groups in the ortho-aryl position and a methyl group in the para-aryl position, activated by diethylaluminum chloride (DEAC), showed highly catalytic activity for the polymerization of ethylene [4.12 Â 10 6 g PE (mol Ni.h.bar) À1 ], and produced highly branched polyethylenes under low ethylene pressure (branching degree: 104, 118 and 126 branches/1000 C at 20, 40 and 60 C, respectively). Chiral 20-electron bis-a-diimine Ni(II) complex rac-2b also exhibited high activity toward ethylene polymerization [1.71 Â 10 6 g PE (mol Ni Á h Á bar) À1 ]. The type and amount of branches of the polyethylenes obtained were determined by 1 H and 13 C NMR. Experimental General Considerations and MaterialsAll manipulations involving air-and/or water-sensitive compounds were carried out with standard Schlenk techniques under nitrogen. Methylene chloride and o-dichlorobenzene were pre-dried with 4 Å molecular sieves and distilled from CaH 2 under dry nitrogen. Toluene, diethyl ether and 1,2-dimethoxyethane (DME) were distilled from sodium/benzophenone under N 2 atmosphere. Anhydrous NiBr 2 (99%) and diethylaluminum chloride (DEAC, 0.9 M solution in toluene) were obtained from Acros. 2,3-Butanedione (98%), 4-methylaniline (98%), 4-chloroaniline (97%), 2,4-dimethylaniline (98%) and 2,4,6-trimethylaniline (98%) were purchased from Alfa Aesar and used without further purification. [NiBr 2 (DME)] was synthesized according to the literature. [20]

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Section: Introductionmentioning

confidence: 99%

New chiral α‐diimine nickel(II) complexes bearing ortho‐sec‐phenethyl groups for ethylene polymerization

Wang

Yuan

Song

et al. 2013

Applied Organom Chemis

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“…[9][10][11][12][19][20][21][22][23][24][25][26][27] In this study, selfassembly of PE-b-PPE copolymers in water was investigated, which is interesting and helpful for a better understanding of potential application in encapsulating hydrophobic drug. Amphiphilic block copolymers have been found to self-assemble spontaneously into polymeric aggregates in selective solvents.…”

Section: Self-assembly Of Pe-b-ppe Copolymers In Aqueous Solutionmentioning

confidence: 99%

“…[13][14][15] Main limitation for synthesis of well-defined polyolefin based amphiphilic copolymers is poor solubility and reactivity of polyolefin block, which largely restricts occurrence of chain extension reaction. [9][10][11][12][21][22][23][24][25][26][27] Highly branched polyethylene with high molecular weight obtained by α-diimine palladium catalyst can be used to construct amphiphilic copolymer, and novel PE based amphiphilic copolymers have been developed. Several noteworthy examples are polyolefin-b-polypeptide, [16][17][18] PE-b-PEO, 19 and polyethylene-b-poly(N-isopropylacrylamide) (PE-b-PNIPAM) block copolymers, 20 the low-molecular-weight of hydrophobic polyolefin building blocks (M n < 5 kg/mol) are obtained by anionic living polymerization of diene or coordination chain transfer polymerization (CCTP).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, characterization and micellization of amphiphilic polyethylene-b-polyphosphoester block copolymers

et al. 2015

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A sequential synthetic strategy combining metal catalyzed living polymerization of ethylene and ring-opening polymerization (ROP) was successfully used to prepare novel polyethylene-block-polyphosphoester (PE-b-PPE) diblock copolymers. Narrowly dispersed hydroxyl-terminated polyethylene (PE-OH) was firstly synthesized by amine-imine nickel catalyzed-living polymerization of ethylene and subsequent chain transfer reaction. PE-b-PPE diblock copolymers with narrow polydispersities were obtained by organocatalyzed ring-opening polymerization (ROP) of 2-ethyoxyl-2-oxo-1,3,2dioxaphospholane or 2-methyl-2-oxo-1,3,2-dioxaphospholane using PE-OH as a macroinitiator. Investigations of selfassembly of the obtained PE-b-PPEs block copolymers in water by means of TEM and laser light scattering confirmed that the amphiphilic block copolymers formed micelles in aqueous solution. These PE-b-PPE block copolymers was used for paclitaxel (PTX) encapsulation to demonstrate the potential in drug delivery. These biocompatible PE-PPE polymeric micelles showed high loading efficiency of 92% and content of PTX of 16.6 wt% as well as slow and sustained release behavior.

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“…An important frontier in the field of polymer synthesis is to develop new methods for the synthesis of polyolefins of defined molecular weight, stereochemistry and consistent composition. In contrast to metallocene catalysts based on early transition metals, Ni(II) and Pd(II) catalysts discovered by Brookhart and co‐workers could produce branched polyethylene with different concentrations and individual length of branches, exclusively from the ethylene monomer and accommodated even polar monomers . However, they generally produce amorphous, atactic polymers .…”

Section: Introductionmentioning

confidence: 99%

Chiral nickel(II) and palladium(II) catalysts bearing strong electron‐withdrawing fluorine groups: synthesis, characterization and their application in catalytic polymerization for ethylene and styrene

Yuan

Zhao

Song

et al. 2014

Applied Organom Chemis

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A series of new chiral and achiral nickel(II) and palladium(II) complexes, {bis [N,N′-(2,6-diethyl-4-naphthylphenyl)imino]-1,2-dimethylethane}dibromonickel 3a, {bis[N,N′-(4-fluoro-2-methyl-6-sec-phenethylphenyl)imino]-1,2-dimethylethane}dibromonickel rac-(RS)-3b, {bis[N,N′-(4-fluoro-6-sec-phenethylphenyl)imino]-1,2-dimethylethane}dibromonickel rac-(RR/SS)-3c and {bis[N,N ′-(4-fluoro-6-sec-phenethylphenyl)imino]-1,2-dimethylethane}dichloropalladium rac-(RR/SS)-3d were successfully synthesized and characterized. The molecular structures of representative ligand rac-(RS)-2b, nickel complex 3a, rac-(RR/SS)-3c and palladium complex rac-(RR/SS)-3d were determined by X-ray crystallography. The structures of complexes 3a and rac-(RR/SS)-3c have pseudo-tetrahedral geometry about the nickel center, showing C 2 molecular symmetry. However, the structure of palladium complex rac-(RR/SS)-3d has pseudo-square planar geometry about the palladium center, showing C 2 molecular symmetry. Complex 3e {bis[N,N′-(2,6-dimethylphenyl)imino]-1,2-dimethylethane}dibromonickel was also synthesized for comparison. Nickel complex rac-(RS)-3b bearing strong electron-withdrawing fluorine group in the para-aryl position and a chiral sec-phenethyl group in the ortho-aryl position of the ligand (one methyl group in the ortho-aryl position) displays the highest catalytic activity for ethylene and styrene polymerization, and produced highly branched polyethylene and syndiotactic-rich polystyrene. However, palladium complex rac-(RR/SS)-3d shows low catalytic activity for ethylene and styrene polymerization due to the poor leaving group, Cl, attached to palladium and the unfavorable molecular structure. [N,N′-(2,6-diethyl-4-naphthylphenyl) Synthesis of bisFormic acid (0.5 ml) was added to a stirred solution of 2,3butanedione (0.09 g, 1.00 mmol) and 2,6-diethyl-4-naphthylaniline (0.61 g, 2.2 mmol) in ethanol (20 ml). The mixture was refluxed for 48 h, then cooled and the precipitate was separated by filtration.Chiral Ni(II) and Pd(II) complexes for ethylene and styrene polymerization

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A ligand exchange strategy for one-pot sequential synthesis of (hyperbranched polyethylene)-b-(linear polyketone) block polymers

Cited by 32 publications

References 36 publications

New chiral α‐diimine nickel(II) complexes bearing ortho‐sec‐phenethyl groups for ethylene polymerization

New chiral α‐diimine nickel(II) complexes bearing ortho‐sec‐phenethyl groups for ethylene polymerization

Synthesis, characterization and micellization of amphiphilic polyethylene-b-polyphosphoester block copolymers

Chiral nickel(II) and palladium(II) catalysts bearing strong electron‐withdrawing fluorine groups: synthesis, characterization and their application in catalytic polymerization for ethylene and styrene

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