Coordination Polymerization in Water Affording Amorphous Polyethylenes

Held, Anke; Mecking, Stefan

Coordination Polymerization in Water Affording Amorphous Polyethylenes

Dateien

2000_Chemistry_Eur_J_6_4623_Mecking.pdfGröße: 185.3 KBDownloads: 710

Datum

2000

Autor:innen

Held, Anke

Mecking, Stefan

URI (zitierfähiger Link)

http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-61936

Link zur Lizenz

Attribution-NonCommercial-NoDerivs 2.0 Generic

Open Access-Veröffentlichung

Open Access Green

Sammlungen

Chemie

Publikationstyp

Zeitschriftenartikel

Publikationsstatus

Published

Erschienen in

Chemistry: A European Journal. 2000, 6(24), pp. 4623-4629

Zusammenfassung

The coordination polymerization of ethylene in water as a reaction medium was studied. Rubbery amorphous branched polyethylene was obtained when a known cationic diiminesubstituted methyl complex was employed as a catalyst precursor. High rates of up to 900 TOhÿ1 (turnover frequency) were observed. In contrast to solution polymerization in an organic solvent, the rate of suspension polymerization in water increases greatly with ethylene pressure in the range up to 20 bar; this indicates control of the polymerization rate by the concentration of the olefin monomer at the catalytically active site. The effect and mode of mass transfer phenomena were studied. A high catalyst stability in the aqueous coordination polymerization was observed. It was found to be due to an "encapsulation" of the water-insoluble catalyst precursor in the hydrophobic amorphous polymer during the polymerization reaction, and this resulted in strongly restricted accessibility for the aqueous phase. Surprisingly, exposure of the water-stable catalyst precursor to ethylene monomer in solution in the presence of water resulted in immediate decomposition. Polymer microstructure, and thermal and mechanical properties were investigated. The different degree of branching, molecular weight, and corresponding macroscopic properties of the polymers obtained in water as a reaction medium versus solution polymerization in methylene chloride under the same conditions are due to the different phase behavior during polymerization (suspension vs. solution), as opposed to an effect of water on the catalytically active centers.

Fachgebiet (DDC)

540 Chemie

Schlagwörter

branched polyethylene, ethylene, palladium, polymerizations, water chemistry

Zitieren

ISO 690

HELD, Anke, Stefan MECKING, 2000. Coordination Polymerization in Water Affording Amorphous Polyethylenes. In: Chemistry: A European Journal. 2000, 6(24), pp. 4623-4629

BibTex

@article{Held2000Coord-9809,
  year={2000},
  title={Coordination Polymerization in Water Affording Amorphous Polyethylenes},
  number={24},
  volume={6},
  journal={Chemistry: A European Journal},
  pages={4623--4629},
  author={Held, Anke and Mecking, Stefan}
}

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