Katalytische Olefinpolymerisation in wässerigen Systemen

Mecking, Stefan; Held, Anke; Bauers, Florian Martin

doi:10.1002/1521-3757(20020215)114:4<564::aid-ange564>3.0.co;2-6

Cited by 32 publications

(6 citation statements)

References 146 publications

(132 reference statements)

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“…This active research field has been accounted recently by a number of excellent reviews. [9,[89][90][91][92] To explain their observed branching formation in PEs, both Brookhart [7] and Fink [85] proposed that the catalyst could isomerize or walk along the polymer backbone during the migratory insertion polymerization. The chain walking of the catalysts is facilitated by a process involving b-hydride elimination and retransfer of the hydride in the opposition regiochemistry (Scheme 5).…”

Section: Background and Mechanism Of Cwpmentioning

confidence: 99%

Recent Progress of Catalytic Polymerization for Controlling Polymer Topology

Guan

2010

Chemistry An Asian Journal

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Catalysis continues to spark new imagination and excitement of synthetic chemists. Discovery of new catalytic processes often makes seemingly impossible transformations proceed magically at high efficiency. In modern polymer synthesis, an exciting direction in recent years is the development of transition-metal-catalyzed polymerizations for controlling polymer topology. In this Focus Review, we highlight a few recent examples for catalytic syntheses of polyolefins having cyclic, block, and dendritic topologies, respectively. These examples showcase the power and efficiency of transition-metal catalysis for accessing various polymer topologies ranging from simple cyclic to complex globular dendritic polymers.

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Section: Background and Mechanism Of Cwpmentioning

confidence: 99%

Recent Progress of Catalytic Polymerization for Controlling Polymer Topology

Guan

2010

Chemistry An Asian Journal

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“…[18,19] More specifically, late-transition-metal catalysts are generally more tolerant of polar functional groups, which allows for relaxed purity requirements of the reaction media, in the more extreme cases even allowing polymerization in aqueous media. [20][21][22] The tolerance for polar functional groups also makes random copolymerization of nonpolar and polar olefins appear to be a realistic objective, [4,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] a goal that is particularly desirable if it can be obtained with the normally quite active and cost-efficient nickel catalysts. [12,[40][41][42][43][44][45][46][47][48][49] Modern catalyst and process technology allows for polymers to be tailored according to specific needs.…”

Section: Introductionmentioning

confidence: 99%

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Heyndrickx¹,

Occhipinti²,

Minenkov³

et al. 2011

Chemistry A European J

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An unconventional chain termination reaction has been explored for the SHOP (Shell higher olefin process)-type, anilinotropone, and salicylaldiminato nickel-based oligo- and polymerization catalysts by using density functional theory (DFT). Starting from the tetracoordinate alkyl phosphine complex, the termination reaction was found to involve a rearrangement of the alkyl chain to form a pentacoordinate β-agostic complex, β-hydride elimination, and olefinic chain dissociation and to compete with propagation at sufficiently high phosphine concentration and/or basicity. It provides the first complete and convincing mechanistic rationale for the decreasing chain lengths observed upon increasing phosphine concentration and basicity. The unconventional reaction was found to be a major termination pathway for the SHOP-type catalyst and is very unlikely to lead to branching and olefin isomerization, which is critical for explaining why the SHOP catalyst, in contrast to the anilinotropone and salicylaldiminato catalysts, tends to lead to the oligomerization of ethylene to form linear α-olefins. Based on our results we have proposed a new and extended catalytic cycle for the SHOP-type ethylene oligomerization catalyst. Finally, the importance of the new termination reaction for the SHOP-type catalyst suggests that this reaction may also operate with other ethylene oligomerization nickel catalysts. This prediction was confirmed for a pyrazolonatophosphine catalyst, for which the new termination route was found to be even more facile, which explains the short oligomers produced by this catalyst.

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“…This process would avoid the need to convert the cracked products to monomers such as acrylates or vinyl esters, which consumes energy and raw materials 3. We and the group of Claverie have recently reported the synthesis and properties of polyethylene dispersions by catalytic polymerization in emulsion 4–6…”

Section: Polymerization Results[a]mentioning

confidence: 99%

Aqueous Dispersions of Extraordinarily Small Polyethylene Nanoparticles

Kolb¹,

Monteil²,

Thomann³

et al. 2004

Angew Chem Int Ed

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General methods and materials. Ethylene of 3.5 grade was supplied by Praxair. Demineralised water was distilled under argon. 2-propanol (p.a.) was degassed by four repeated freeze-thaw cycles. Chloranil (Aldrich) und sodium dodecyl sulfate (Fluka) were used without further purification. Potassium 4-(diphenylphosphino)benzenesulfonate (TPPMS) was synthesized as described in [1]. bis (1,5-cyclooctadiene) nickel was synthesized according to [2] (the compound is also available commercially, e.g. at Aldrich or Strem). TEM investigations were carried out on a LEO 912 Omega apparatus using an acceleration voltage of 120 kV. Samples were stained with RuO 4 . For microtome cutting, the latex particles were embedded in nanoplast ® (a hydrophilic melamine resin). Microtome cuts of ca. 50 nm thickness were prepared with a Reichert & Jung Ultracut E microtome equipped with a 45° diamond knife supplied by Diatome. AFM experiments were performed with a Nanoscope III scanning probe microscope. The height and phase images were obtained simultaneously while operating the instrument in the tapping mode under ambient conditions. Images were taken at the fundamental resonance frequency of the Si cantilevers which was typically around 180 kHz. Typical scan speeds during recording were 0.3-1 line/s using scan heads with a maximum range of 16 × 16 µm. The phase images represent the variations of relative phase shifts (i. e. the phase angle of the interacting cantilever relative to the phase angle of the freely oscillating cantilever at the resonance frequency) and are thus able to distinguish materials by their material properties (e.g. amorphous and crystalline polymers). DSC was performed on a Perkin Elmer DSC 7 instrument or on a Pyris 1 DSC at a heating and cooling rate of 10 K min -1 . T m data reported are local maxima of the second heats. DSC traces of polymer dispersions were obtained on 20 to 30 mg of dispersion with ca. 5 % by weight polymer content. NMR spectra were recorded on a Bruker ARX 300 instrument ( 1 H: 300 MHz; 13 C: 75 MHz). 1 H and 13 C NMR spectra were performed in 1,1,2,2-tetrachloroethane-d 2 at 122 °C. GPC analyses were carried out by Basell GmbH, Ludwigshafen on a Waters150 or GPC2000 instrument equipped with Shodex columns at 140 °C in 1,2,4-trichlorobenzene. Data is referenced to linear polyethylene standards. Dynamic light scattering on dispersions was performed on a Malvern particle sizer.Catalyst Preparation. The preparation of catalyst was performed by standard Schlenk techniques under argon. Equal molar amounts of chloranil and TPPMS were dissolved in a given amount of 2-propanol (2 to 10 mL). The obtained yellow solution was transferred to a 1.1-fold molar excess of bis(1,5-cyclooctadiene)nickel. Polymerization Procedure. Polymerization was carried out in a mechanically stirred 250 mL pressure reactor equipped with a heating/cooling jacket, the temperature being controlled automatically by means of a sensor dipping into the reaction mixture. Ethylene consumption during polymerization was followed b...

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Katalytische Olefinpolymerisation in wässerigen Systemen

Cited by 32 publications

References 146 publications

Recent Progress of Catalytic Polymerization for Controlling Polymer Topology

Recent Progress of Catalytic Polymerization for Controlling Polymer Topology

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Aqueous Dispersions of Extraordinarily Small Polyethylene Nanoparticles

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