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Coordination polymerization in water affording amorphous polyethylenes
1Institut für Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universität Freiburg, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|February 24, 2001
Summary
Coordination polymerization of ethylene in water yields branched polyethylene at high rates. Catalyst stability is achieved through polymer encapsulation, preventing decomposition in the aqueous medium.
Area of Science:
- Polymer Chemistry
- Catalysis
- Materials Science
Background:
- Coordination polymerization typically occurs in organic solvents.
- Ethylene polymerization in aqueous media presents challenges due to catalyst stability and monomer solubility.
- Developing environmentally benign polymerization processes is a key research area.
Purpose of the Study:
- To investigate the coordination polymerization of ethylene in water using a cationic diimine-substituted methyl complex.
- To understand the factors influencing polymerization rate, catalyst stability, and polymer properties in an aqueous medium.
- To compare the outcomes of suspension polymerization in water with solution polymerization in an organic solvent.
Main Methods:
- Utilized a cationic diimine-substituted methyl complex as a catalyst precursor for ethylene polymerization.
- Conducted polymerization in water as a suspension medium and in methylene chloride as a solution medium.
- Analyzed polymer microstructure, thermal properties, and mechanical properties.
- Investigated mass transfer phenomena and catalyst stability.
Main Results:
- Achieved high polymerization rates (up to 900 turnover frequency) producing rubbery amorphous branched polyethylene.
- Observed increased polymerization rates with ethylene pressure in water, indicating monomer concentration control at active sites.
- Demonstrated high catalyst stability in water attributed to encapsulation within the hydrophobic polymer, restricting aqueous phase access.
- Found that polymer properties differ due to suspension vs. solution phase behavior, not water's effect on active centers.
Conclusions:
- Coordination polymerization of ethylene in water is feasible, yielding branched polyethylene with distinct properties.
- Catalyst stability in aqueous suspension polymerization is enhanced by polymer encapsulation.
- The phase behavior during polymerization significantly influences polymer microstructure and macroscopic properties.