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Addition Polymerization (Chain Growth) Step Growth Polymerization (Condensation)

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Diferences between step-growthpolymerization and chain-growth

polymerizationStep-growth polymerization Chain-growth polymerization

Growth throughout matrix Growth by addition of monomeronly at one end of chain

Rapid loss of monomer early inthe reaction

Some monomer remains e en atlong reaction times

Same mechanism throughout !i"erent mechanisms operate atdi"erent stages of reaction (i#e#

$nitiation% propagation andtermination)

A erage molecular weightincreases slowly at low

con ersion and high extents ofreaction are re&uired to obtain

high chain length

'olar mass of bac bone chainincreases rapidly at early stageand remains approximately the

same throughout thepolymerization

nds remain acti e (notermination)

Chains not acti e aftertermination

*o initiator necessary $nitiator re&uired

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Steps of Radical Chain

Polymerization

$nitiation

Propagation

+ermination

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$*$+$A+$,*

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PR,PAGA+$,*

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C.A$* +RA*S/ RR AC+$,*S

+ransfer to monomerreaction

+ransfer to initiator reaction

+ransfer to sol ent reaction

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$,*$C C.A$* P,01' R$2A+$,*3sing catalyst% not initiator

.ighest reaction rate

+ermination step is 4ust disproportionation

n ironment must be pure

Reaction occurs in the cold

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nionic Polymerization50i ing Polymerization$f the starting reagents are pure and

the polimerization reactor is purged of all

oxygen and traces of water% polimerization

can proceed until all monomer is

consumed#

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C,*! *SA+$,*P,01' R$2A+$,*

3sing catalyst

'inumum two functional groups re&uired

3sually linear

'olecular weight increases slowly at low

con ersion

.igh extents of reaction are re&uired to obtain

high chain length

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6$* +$CS ,/

P,01' R$2A+$,*Reaction rate of ionic polimerization more

than radicalic polimerization

So inetics of ionic polimerization are not

calculated

7ut inetics of radicalic polimerization can beanalysed

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6inetic of RadicalicPolymerization

$nitiation-

Propagation-

+ermination-

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6inetic of RadicalicPolymerization

Ro 5 o erall rate of

polimerization

Rp 5 rate of chainpropagation

R i 5 rate of

initiation step

R t 5 rate of

termination step

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6inetic of Condensation

Polymerization&ui alent

reacti ity of

functional groups#

$t may be 8rst%

second or third

order by

depending upon#

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6inetic of Condensation

Polymerization

Assumption 5 a stoichiometry balance of monomer concentration