Polymers

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Polymers

• Stereoregularity and Properties

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Polymers

• Large volume thermoplastics
• Polyethylene
• Polypropylene
• Polystyrene
• Poly(vinyl-chloride)

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PolypropyleneStereoregularity
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PolypropyleneStereoregularity
Polymer tacticity influences the degree to which
it has rigid, crystalline long range order or
flexible, amorphous long range disorder.
Melting point Solubility Mechanical properties
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Metallocene Catalysts

• Titanocene and Zirconocene Catalyst (Natta 1962)
• atactic
• Ansa Zirconocenes (Kaminsky, 1985)
• isotactic and syndiotactic
• Commercial production of syndiotactic PP (Fina
  1988)
• Cs symmetric catalysts (14-19)
• Isospecific catalysts
• C2 (5-10)

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Metallocene Catalysts

• The ability to rationally design the metallocene
  catalysts result in the ability to control
  polymer microstructure.

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PolypropyleneModel the different stereoregular
polymers and correlate with physical properties
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Properties
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Other functional groups

• How does the R group affect structure?
• Electronics?
• Thermodynamics?

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PolypropyleneC91H184

• Isotactic, syndiotactic, atactic
• Interface WebMO
• MOPAC
• Geometry optimization
• Semi-empirical calculation
• PM3

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Configurations and Polystyrene
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Energies

• Used MMFF94 in ChemBio3D Ultra
• Styrene 22.529 kcal/mol
• Head-to-head (28 mers) 58.93 kcal/mer
• Head-to-tail (28 mers) 30.45 kcal/mer
• HH HT ? 28.55 kcal/mer
• Heat of Reaction HH 36.40 kcal/mer
• HT 7.59
  kcal/mer
• One literature value -17.88 kcal/mer
• Need to rethink signs (and in literature)

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Which is which??
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Conformation

• 30carbon atoms in polyethylene

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(No Transcript)
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And the Results Are