Chapter 10. Step-Reaction and Ring-Opening
Polymerization
10.1 Introduction
10.2 Step-reaction polymerization---Kinetics
10. 3 Stoichiometric Imbalance.
10. 4 Molecular weight Distribution
10. 5 Network Step Polymerization
10. 6 Step-Reaction Copolymerization.
10. 7 Step polymerization Techniques.
10. 8 Dendritic Polymers.
10. 9 Ring-opening polymerization.
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10.1 Introduction
A. Characteristics of step-reaction polymers.
a. Polymers containing functional group in backbones
b. Synthesizing dendritic polymers
B. Examples of commercialized step-reaction polymers.
Note) Table 10.1
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10.2 Step-reaction polymerization---Kinetics
A. Types of monomer
a. AB type
HO
COOH
b. AA and BB type
HOOC
COOH
HOCH2CH2OH
c. Three functional group for crosslinked polymers
HOCH2CHCH2OH
OH
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10.2 Step-reaction polymerization---Kinetics
B. Condensation of difunctional monomers.
a.
b.
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C. Kinetics of step-polymerization.
a. Assumption : Independence on chain length.
b. Rate equation and
A
+ B
d [ A]

 k[ A][ B]
dt
Integration
Polymers
condensation
[ A]  [ B]
d [ A]
2

 k[ A]
dt
1
1

 kt
[ A] [ Ao]
Combining Carothers equation.
DP  [ Ao]kt  1
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C. Kinetics of step-polymerization.
c. Polyesterification : self-acid catalyzed reaction.

d [ A]
 d [ A]3
dt
Integration
1
1

 2kt
2
2
[ A] [ Ao ]
Combining Carothers equation.
DP 
2
 2kt[ Ao ]2  1
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10. 3 Stoichiometric Imbalance.
A. Chain length control.
a. High molecular weight.
b. Oligomers for free polymer.
1) Epoxy oligomer.
2) Unsaturated polyester.
3) Polyamide
B. Preparing methods for oligomers.
a. Quenching : unsaturated polyester.
b. Stoichiometric imbalance : epoxy resin.
c. Addition of monofunctional reactant.
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10. 3 Stoichiometric Imbalance.
C. Modification of Carothers equation.
a. parameter r : stoichiometric imbalance.
N Ao
r o
NB
N Ao , N Bo : initial unreacted groups.
N A  (1  p) N Ao
N Ao
N B  (1  p) N  (1  pr )
r
o
B
1 r
DP 
r  1  1rp
if
N A, N B
r  1 , then
if
p 1
: unreacted group.
1
: Carothers equation.
DP 
1 p
, then
1 r
DP 
1 r
10. 4 Molecular weight Distribution
A. Conversion and Nx
No  N
p
No
N x  Np x 1 (1  p)
10. 4 Molecular weight Distribution
B. Conversion and Wx
xNx M o xNx
Wx 

No M o
No
Wx  x(1  p ) p
2
x 1
C. Polydispersity index
Mo
Mn 
1 p
M o (1  p)
Mw 
1 p
Mw
PI 
 1 p
Mn
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10. 5 Network Step Polymerization
A. Greater than two functionality polymers.
a. Alkyd-type polyester :
OH
HOCH2CHCH2OH
OH
b. Phenol-formaldehyde resin :
c. Melamine-formaldehyde resin :
NH2
N
H2N
N
N
NH2
10. 5 Network Step Polymerization
B. Gelatin : High conversion of greater than two functionality.
a. Gel point : onset of gelatin.
sudden increase in viscosity.
change from liquid to gel.
bubbles no longer rising.
impossible stirring.
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10. 5 Network Step Polymerization
C. Gel point conversion.
No  N
p
No
2
pc 
f av
pc : critical reaction conversion.
f av : average functionality.
pc 
1
[r  r   


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10. 5 Network Step Polymerization
D. Examples of gel point conversion.
O
O
OH
HOCH2CHCH2OH
O
3mol of 1
2mol of 4
(3  2)  (2  3)
f av 
 2. 4
5
Gel point conversion : 77% (Experiment)
83% (Calculate)
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10. 6 Step-Reaction Copolymerization.
A. Random copolymers.
1:1:2 mixture of terephthalic acid, isophtahlic acid, ethylene glycol.
B. Alternating copolymers.
a.
b. Randomization : Trans-esterification.
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10. 6 Step-Reaction Copolymerization.
C. Block copolymer.
Telechelic polymers.
a.
b.
c.
10. 7 Step polymerization Techniques.
A. Significant difference between vinyl and nonvinyl polymerization.
a. Vinyl polymerization : Large enthalpy factor.
Exotherm reaction.
b. Nonvinyl polymerization : High activation energy.
Low exotherm.
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10. 7 Step polymerization Techniques.
B. Step polymerization techniques.
a. Bulk polymerization.
1) Advantage : Free of contaminants.
2) Disadvantage : High viscosity.
b. Solvent polymerization.
1) Advantage : Lower viscosity.
Removing by products by azeotropic distillation.
2) Disadvantage : Solvent removing process.
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10. 7 Step polymerization Techniques.
c. Interfacial polymerization.
Polymerization at the interface between immiscible two solvents.
Water : Diamine.
Organic solvent : Diacid chloride.
1) Low temperature polymerization.
2) Rapid polymerization.
3) Higher molecular weight.
4) Not necessary stoichiometric balance.
․Schotten-Baumann reaction.
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10. 7 Step polymerization Techniques.
d. Phase-transfer catalysis polymerization(PTC).
1) Phase-transfer catalyst : Benzyltriethylammonium chloride.
C6H5CH2N+(C2H5)3Cl2) Mechanism : Dissolve in water and make ion pair.
Move to organic layer.
10. 8 Dendritic Polymers.
A. Terminology (Since 1980s)
Dendrimer : Dendron = like tree.
Starburst polymer.
B. Commercial application.
a. Drug delivery system : Controlled release of agricultural chemicals
b. Molecular sensors.
c. Rheology modifiers.
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10. 8 Dendritic Polymers.
C. Characteristics feature.
a. Structure : Three component parts.
1) Core.
2) Interior dendritic structure.
3) Exterior surface.
b. Easy control macromolecular dimension by a repetitive sequence of step.
c. More soluble than linear polymer : high surface functionality.
d. Low viscosity : No entanglement.
e. Supramolecular assembly : Guest molecules among the interior branches
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10. 8 Dendritic Polymers.
D. Synthsis of dendrimer.
a. Divergent :
1) Polyamidamine (PAMAM).
2)
10. 8 Dendritic Polymers.
b. Convergent.
10. 8 Dendritic Polymers.
E. Hyperbranched polymer.
a. Types of monomer : AxB ( x > 1).
F. Nanostructure of dendrimer.
a. Molecules dimension : 1-100nm.
b. Molecules devices : Mimicking nanoscopic biomolecules.
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10. 9 Ring-opening polymerization.
A. Commercially important ring-opening polymers.
Ring-opening polymers : Condensation polymers.
Not polycondensation reaction.
No byproduct.
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B. Mechanism of ring-opening polymerization.
a. Initiator : Ionic or coordination species (X*).
1)
2)
b. Initiator : XY.
1)
10. 9 Ring-opening polymerization.
C. Ring strain : Possibility of ring-opening polymerization.
3>4>8>7>5>6
D. Ring-opening block copolymerization.
AB, [AB] , ABA Block copolymer.
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