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Chain and Step GrowthPolymerization

Brazel & Rosen 8.1

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• Four chain growth mechanisms– Free radical

– Cationic

– Anionic

– Coordination

Chain Growth (Addition) Polymerization

I . + M M

.

C=CHH H

+

carbocation

CR1

R2

R3

¨

M-C

carbanion

Dissolve in THF, acetone, DMF, DCM, DMSO

Dissolve in formic acid, IPA, EtOH, MeOH

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Stages of Chain Growth

• Initiation

• Propagation

• Termination

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Mechanisms of Termination• Combination

• Disproportionation– H abstraction

• Chain Transfer– Abstraction– backbiting

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Step Growth (Condensation) Polymerization

• Polycondensation– Bifunctional monomers of different species react

to form new molecule plus some byproduct

– Polyester

– Nylon 6,6

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Step Growth (Condensation) Polymerization

• Self-condensation– Polycaprolactone

• Exceptions to condensation rule– Polyurethane

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Polymers formed by step growthpolymerization

• Aliphatic polyimides• Polyaramids• Polyesters• Polyethylene terephthalate• Polyurethanes• Polycarbonates• polyimides

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