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Olefin Polymerizations Catalyzed by Late Transition Metal Complexes. Maurice Brookhart University of North Carolina. Polyolefins. Total : 100 billions / year 16lbs / person on Earth / year !. Inexpensive monomers Little waste in production

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Olefin Polymerizations Catalyzed by Late Transition Metal Complexes

Maurice Brookhart

University of North Carolina

slide2

Polyolefins

Total : 100 billions / year

16lbs / person on Earth / year !

  • Inexpensive monomers
  • Little waste in production
  • Attractive physical properties, long term stabilities
slide3

Polymer Microstructure — Key to Properties

Polypropylene

Tm = 160°C

Stereoregular

Tm = 165°C

Completely amorphous

Polyethylene

  • High Density PE (HDPE) Tm= 136°C
  • Linear Low Density PE (LLDPE)
          • Tm = 115~130°C
  • Low Density PE (LDPE) Tm= 105~115°C
slide4

Polyolefins Primarily Produced via Metal-Catalyzed Processes

  • Catalyst Structures Control:
    • polymer microstructures
    • polymer molecular weights, molecular weight distributions
    • comonomer incorporation

Late Metal Catalysts (Pd, Ni, Co)

Early Metal Catalysts (Ti, Zr, Cr)

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Olefin Polymerizations Using Late Metal Catalysts (Ni, Pd)

  • Why Late Metals ?
  • Potentially different enchainment mechanisms =>
      • new microstructures
  • Less oxophilic — functional group compatible
  • But…
  • Normally lower insertion barriers
  • Chain transfer competitive with propagation =>
    • dimers, short chain oligomers
diimine based catalysts
α–Diimine Based Catalysts

■ High molecular weight polymers with unique microstructures from:

● ethylene

● α – olefins

● cyclopentene

● trans-1,2-disubstituted olefins

■ Copolymers of ethylene with certain polar vinyl monomers

commercial copolymers of ethylene and polar vinyl monomers
Commercial Copolymers of Ethylene and Polar Vinyl Monomers

● Radical Initiation

● High temperatures, very high ethylene pressure

examination of pd and ni diimine catalysts for copolymerizations of ethylene and
Examination of Pd and Ni Diimine Catalysts for Copolymerizations of Ethylene and:
problems connected with copolymerization
Problems Connected with Copolymerization

1. Monomer Binding through the Functional Group

2. β-Elimination of G

slide28
3. Weak Competitive Binding of

4. Strong Chelate Formation Following Insertion

examination of pd and ni diimine catalysts for copolymerizations of ethylene and33
Examination of Pd and Ni Diimine Catalysts for Copolymerizations of Ethylene and:
advantages of vinyl alkoxy silane comonomers
Advantages of Vinyl Alkoxy Silane Comonomers
  • Insertion barriers of vinyl alkoxy silanes into Pd-R and Ni-R bonds are similar to ethylene insertion barriers.
  • Chelates resulting from vinyl alkoxy silane insertions are readily opened with ethylene.
  • Open chelates readily insert ethylene.
  • Relative binding affinities favor ethylene, but not to a prohibitive extent.