Spring 2007
Chap 8. Polycondensation Reactions
Classification by Mechanism
 Step – Growth
 Chain – Growth
Classification by Type
 Condensation
 Addition
Surfing to the internet
Classification by Bond
 Radical
For further details,
Click next homepage.
http://www.pslc.ws/mactest/synth.htm
 Ion
Hanyang Univ.
Spring 2007
What are differences between step and chain growth polymerizatoin?
Step Growth Polymerization
• The growing chains react with each other.
Radical
• Polymers frwo to high Mw at a slow rate.
• High Mw is formed at the end of polymerization.
−
Mn
Living
• Long reaction time is needed to obtain high Mw and high conversion
Step Growth
Chain Growth Polymerization
• Monomer molecules add on to a growing polymer chain one at a time.
100
0
% Conversion
• Polymers grow to high Mw at a very fast rate
• High Mw is formed at the early stage.
• Monomer adds on the growing polymer chain via reactive active center.
Hanyang Univ.
Spring 2007
Addition versus Condensation polymerisation
• Condensation polymers (C): fewer atoms in the
backbone because of formation of by-products
HO
O
O
O
2
OH
+
H2N
6
NH2
*
O
4
N
H
6
• Addition polymers (A): the repeating unit contains
the same atoms as the monomer
n
*
*
n
*
O
O
*
O
O
Hanyang Univ.
N
H
n
*
Spring 2007
Characteristics of Step-Growth
Step-growth polymerization principle was used by Carothers in 1929.
Synthesis of Ester
O
O
HO C
CH2CH3
OH CH2CH3
CH3 CH2 C
O
CH2CH3
Carothers thought about following reaction.
R macromolecules
O chainlike
O
ItOseemedOto him more likely that one would get long
like this
Many scientists were sure that one
OH C R C OH
OH
R'
OH
O
R'
O
would get a ring-like molecule
But, if more acid and alcohol were used, ring would not form because of unstability of ring-shaped
molecules more than six atom.
Hanyang Univ.
Spring 2007
Characteristics of Step-Growth
JACS (Journal of American Chemical Society, 51, P. 2548 (1929))
“Polyintermolecular condensation requires as starting materials
compounds in which at least two functional groups are present in
the same molecule”
O
O
OH C R C OH
OH
R'
OH
Hanyang Univ.
Spring 2007
Equal Functional Group Reactivity Concept
Extended by Flory
The reactivity of functional group is not correlated with complexity and size of molecule with
functional group.
HO R OH
HO
HO R OH
R OH (size)
+
HOOC R' COOH (complexity)
This concept is useful to polycondensation type polymerization.
ex) OCNRNCO + H2NR`NH2  polyurea
Hanyang Univ.
Spring 2007
Equal Functional Group Reactivity Concept
This concept also can be applied to Chain-growth polymerization.
Olefins
Vinyl monomers
Unsaturated monomers
H
H
H
C C
H
H H
OR
H
C C OR
H
C C
H
H
H H
H H H H H
C C C C C OR
H H H H H
So, double bond in vinyl monomer is considered as bifunctional.
Hanyang Univ.
Spring 2007
Equal Functional Group Reactivity Concept
I. Thermodynamic Approach
“In order to for a polymerization to be thermodynamically feasible, the
Gibbs-Free Energy change must be negative, that is, ΔGp < 0.”
G = HTS
GP = HPTSP : this equation is the basic of understanding about polymerization,
depolymerzation equilibrium
Hanyang Univ.
Spring 2007
Equal Functional Group Reactivity Concept
GP = Gpolymer  Gmonomer
= (HP – Hm) – T(SP – Sm)
= HP – TSP
Where HP : enthalpy change per monomer unit
SP : entropy change per monomer unit
GP < 0  Polymerization is spontaneous
GP > 0  Polymerization is not possible
GP = 0  monomer polymer
at this temperature is ceiling temperature.
(for both step and chain growth)
Hanyang Univ.
Spring 2007
Equal Functional Group Reactivity Concept
II.Kinetic Approach
“A negative GP does not necessarily mean that polymerization occurs under
a particular set of reaction conditions and reaction sites”
e.g) should have
 functional group
 proper initiator
 temperature etc.
Hanyang Univ.
Spring 2007
Step Growth Polymerization
Stage 1
n
n
Consumption
of monomer
Stage 2
Combination
of small fragments
Stage 3
Reaction of
oligomers to give
high molecular
weight polymer
Hanyang Univ.
Spring 2007
Step Growth Polymerization
1. Polyesterification by esterinterchange
O
O
x HO R OH + xR"OCR' C O R"
O
O
R" (OCR' C O R ) xOH + (2 x 1)R" OH
2. Polyesterification and polyamidation by Schotten-Baumann Reaction
OH
O
+
C Cl
NH2
Hanyang Univ.
Spring 2007
Step Growth Polymerization
3. Amidation by thermal dehydration of ammonium salt
n H2N(CH2)6 NH2 + n HOOC(CH2)4 COOH
n
OOC(CH2)4 COO
+
+
H3N(CH2)6 NH3
H
NH (CH2)6 NH CO
(CH2)4 CO
OH +
n
(2n 1) H2O
4. Reaction of OCNRNCO + HOR’OH  polyurethane
H2NR’NH2  polyurea
Hanyang Univ.
Spring 2007
Step Growth Polymerization
Well-studied, well characterized rexns
Well-understood rexns at least on an empirical basis.
OH
+
high MW, linear?
CH2O
polyfunctional
OH
O
OH
CH2
CH2
O
Surfing to the internet
CH2
CH2
For further details,
Click next homepage.
X-linked, inefficient rexn.
http://www.chemheritage.org/EducationalSe
rvices/nylon/other/step/step.html
Hanyang Univ.
Spring 2007
Carother’s Equation
W. Carothers
In step-growth polymerization, Carother's equation gives the number-average degree of
polymerization, Xn, for a given fractional monomer conversion, p.
M  M 0  1  P 
M 0   1
N
DPn  0 
M 1  P
N
P = extent of reaction
[M]= concentaration of monomer
1
DPn 
 Carother' s eq.
1 P
P
0
0.5
0.8
0.95
0.99
0.999
DPn
1
2
5
50
100
1000
When P = 0.995 DPn = 200.
Hanyang Univ.
Spring 2007
Carother’s Equation
P
The number of funtional groups used 2( N 0  N)

(1)
Number of functional groups initially
N 0f
DPn 
Initial number of monomers
N
 0 (2)
Number of moles of molecules after reaction
N
f = number of average functional group per monomer
N0 = number of initial monomers
N0f = number of initial functional group
N = number of final molecules (monomer, dimer,  polymer)
From eqn (1) (2)
P
2
2

f DPn  f
 DPn 
2
1

if f  2
2  fP 1  P
Generalized Carother's Eq.
Hanyang Univ.
Spring 2007
Carother’s Equation
ex) monomer=10, fg= 20
final molecules= 2
2(10 - 2) 8
  0.8
2 10
10
1
DPn 
5
1  0.8
DPn is number of S.U (if S.U  R.U then R.O)
P
Surfing to the internet
For further details about W.Carothers
Click next homepage.
http://www.chemheritage.org/EducationalServic
es/chemach/pop/whc.html
Hanyang Univ.
Spring 2007
Four Requirements of Polycondensation
DPn  200
Polymer yield = 99.5%
P = 0.995
 Highly efficient Reaction
 Absent of side Reactions
that is, a 99.5% consumption of functional group does not necessarily a 99.5% polymer yield or
99.5% yield of interunit linkages
Ex)
HO (CH2)5 COOH
HO (CH2)4 CH3
+
CO2
-CO2
 High monomer purity
 Exact (on known) Stoichiometry
Exact (on known) equivalence of functional groups.
Molecular Weight Control of Polycondensation Reaction
Equivalence of Functional Groups.
Hanyang Univ.
Spring 2007
Kinetics (ref. chap 11 in book)
A. Types of monomer
a. AB type
HO
COOH
b. AA and BB type
HOOC
COOH
HOCH2CH2OH
c. Three functional groups for crosslinked polymers
HOCH 2CHCH 2OH
OH
Hanyang Univ.
Spring 2007
Kinetics (ref. chap 11 in book)
B. Condensation of difunctional monomers.
a.
O
HOCH2CH2OH
H+
O
(-H2O)
*
OCH2CH2
*
O
b.
NH
H2NCH2CH2CH2CO2H
∆
O
(-H2O)
*
NHCH2CH2CH2C
*
Hanyang Univ.
Spring 2007
Kinetics (ref. chap 11 in book)
Polyesterfication as an example of polycondensation
k
COOH
OH
O
CO
- d[COOH] / dt = k [COOH][OH][acid]
Assumption : without strong acid catalyst condition, pure monomer and correct equivalent
- d[COOH] / dt = k3[COOH]2[OH]
-COOH is considered as acid catalyst
- d[COOH] / dt = k3[COOH]3
[COOH] = [OH]
integral eqn
1 / [COOH]2 = 1 / [COOH]02 +2k3t
1 / (1-P)2 = 1+2[COOH]02k3t
P = 1 – [COOH] / [COOH]0
Hanyang Univ.
Spring 2007
Kinetics (ref. chap 11 in book)
Assumption : with strong acid catalyst condition, pure monomer and correct equivalent
- d[COOH] / dt = [COOH]2(k3[COOH] + kcat[ H +] )
kcat » k3
k3 can be neglected.
-d[COOH] / dt = k2[COOH]2
k2 = kcat[H+]
integral eqn
1 / (1-P) = 1 + k2[COOH]0 · t
DPn 
1
1 P
[COOH] = [COOH]0 (1-P)
DPn  1  [COOH]0 k2 t
If you know the value of K2, you can calculate DPn at any time
Hanyang Univ.
Spring 2007
Kinetics (ref. chap 11 in book)
ex)
k 2  10 –2 l mole1sec1 , C0  3 mole  sec  l1 , DPn =50
( k2 = kcat[H+] )
Reaction time = ? less than 30 min
if k 2  10 –4 l mole1sec1
Reaction time = ? about 45 hr
Hanyang Univ.
Spring 2007
Kinetics
Mw distributions of linear condensation polymers
Assumption : Independence between reaction time and molecular size
P:
fraction of functional groups that have reacted in time t
1-P :
fraction of functional groups remaining at time t
x-mer: randomly selected polymer molecule containing exactly x structural units.
Probability finding a reacted carboxyl group in molecules = P
Probability finding (x-1) number of reacted carboxyl group in molecules = P x1
Probability finding a unreacted carboxyl group in molecules = 1P
Probability finding
x-mer = P x1(1-P)
Hanyang Univ.
Spring 2007
Kinetics
If there are N number of molecules, total x-mer number is
N x = N  P x1(1-P)
N = N 0 (1 P)
 N x = N 0  P x1(1P) 2
 Mw distributions of linear condensation polymers .
0.045
P=0.95
Nx
0.020
P=0.98
0.010
P=0.99
100
220
Hanyang Univ.
Spring 2007
Kinetics
DPn   x  N x
Wx 
x 1
xp


DPw   x  Wx
xw 
1 p
1 p
DPw
 1 P
DPn
x  Nx
 x  (1  p) 2  p x -1
N0
x
2
p x 1
x
3
x 1
odian page 79
2.0
p
1
(1  P) 2
1 P

(1  P) 3
1  4P  P 2

(1  P) 4
MWD
Hanyang Univ.
Spring 2007
Molecular Weight Control
Target Molecular weight
DPn is time – dependent
1) Quench (cooling) the polymerization at pre- determined time
heating
HO
R
unstable
COOH
HO
HOOC
COOH
OH
react as heating  undesirable
Hanyang Univ.
Spring 2007
Molecular Weight Control
2) Regulation of monomer concentration
nonstoichiometric condition or adding monofunctional reactant.
HO
R
OH
+
HOOC
R'
COOH
HOOC
COOH
HOOC
COOH
EXCESS
• Stable Polymer
• No more reaction.
can control & limit MW
Hanyang Univ.
Spring 2007
Molecular Weight Control
Nylon 66: Adding lauric acid or acetic acid, MW control
Possible melt spinning through viscosity control
melt
viscosity
undesirable
mw
Hanyang Univ.
Spring 2007
Molecular Weight Control
Assume B-B unit slightly in excess
NA : number of A functional group
Nb : number of B functional group
r = NA / Nb = feed ratio
P : rate of A group at t
rP : rate of B group at t
Initial total number of molecules = (NA + NB) / 2
Number of unreacted A= NA(1―p)
Number of unreacted B= NB(1―rP)
Number of total chain end = Number of unreacted A and B
→ Number of total molecules after t = (Number of total chain end )/2
= [NA(1―p)+ NB(1―r p)]/2
Hanyang Univ.
Spring 2007
Network Step Polymerization
A. Greater than two functionality polymers.
a. Alkyd-type polyester :
OH
HOCH 2CHCH 2OH
OH
b. Phenol-formaldehyde resin :
NH 2
c. Melamine-formaldehyde resin :
N
H2N
N
N
NH 2
Hanyang Univ.
Spring 2007
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.
Hanyang Univ.
Spring 2007
Network Step Polymerization
C. Gel point conversion.
No  N
p
No
pc 
2
f av
pc : critical reaction conversion.
f av : average functionality.
pc 
1

[r  r    
Hanyang Univ.
Spring 2007
Network Step Polymerization
D. Examples of gel point conversion.
O
O
OH
HOCH 2CHCH 2OH
O
3mol of 1
2mol of 4
(3  2)  (2  3)
f av 
 2.4
5
Gel point conversion : 77% (Experiment)
83% (Calculate)
Hanyang Univ.
Spring 2007
Carother’s Equation
where DPn ∝
DPn ∞
f avg 
N f
N
pc 
i i
i
Ni:Monomer have functional group, f i
favg
12

 2.4 ex) 2mole Glycerol 6OH
5
3mole Phthalic Acid 6COOH
total 5 mole
2
f avg
= critical extent of reaction at gel point
In case of ex.
Pc = 2/2.4 = 0.833
12 f.g
N, No , No favg=total functional group
2( No- N) = number of functional
2( N 0  N )
P
N 0  f avg
DPn 
group after reaction
N0
2

N 2  pf avg
Hanyang Univ.
Spring 2007
Example of condensation polymerization
A. Polyester
(Dacron, Mylar) ester interchange rexn is faster than direct esterification.
It is difficult to purify diacid.
Methyl ester is used commonly.
For termination, alcohol is removed by distillation of reaction mixture.
Surfing to the internet
For further details about Polyester
Click next homepage.
http://www.pslc.ws/mactest/pet.htm
Hanyang Univ.
Spring 2007
Example of condensation polymerization
O
O
1.
CH3OC
2 HO(CH2)2OH
O
O
HOCH2CH2OC
2.
+
COCH3
COCH2CH2OH
+
2 CH3OH
O
O
n HOCH2CH2OC
COCH2CH2OH
O
HOCH2CH2O-C
O
H
COCH2CH2O
+
(n-1) HOCH2CH2OH
n
Hanyang Univ.
Spring 2007
Example of condensation polymerization
B. Nylon 66
.
 nylon salt
n H2N (CH2)6 NH2
+
n HOOC(CH2)4COOH
n
- O C(CH ) CO 2
2 4
2
+H N(CH ) NH
3
2 6
3
H
N (CH2)6 N
H
H
O
O
C
(CH2)4 C
OH
+
(2n-1) H2O
Surfing to the internet
For further details about Nylon
Click next homepage.
http://www.pslc.ws/mactest/nysyn.htm
http://www.pslc.ws/mactest/nylon.htm
Hanyang Univ.
Spring 2007
Example of condensation polymerization
C. Aromatic Polyamide
Kevlar
H2N
poly(p-phenylene terephthalamide)
-high strength
NH2
+
HOOC
COOH
HN
O
O
NHC
C
n
Surfing to the internet
For further details about Kevlar and Nomex
Click next homepage.
http://www.pslc.ws/mactest/aramid.htm
Hanyang Univ.
Spring 2007
Example of condensation polymerization
Nomex poly(m-phenylene isophthalamide)
-very good high temperature resistance
HOOC
NH2
H2N
+
COOH
-HCl
-H2O
CH2Cl2
DMAc
The electron density of NH2 is reduced by aromatic ring. So, the nuclephilicity of aromatic
amine is reduced by –COOH.
High temperature is needed.
For faster reaction, diacid chloride is used.
* Coordinated covalent bond by using Li ion
Li
C O
C
O
Hanyang Univ.
Spring 2007
Example of condensation polymerization
D. Aromatic Polyimides
O
O
n O
+
O
O
n H2N
DMAc
DMF
DMSO
O
p-aminoaniline
Pyromellitic dianhydride
(PMDA)
O
O
C NH
[
N ]
H
n
-H2O
COOH
HOOC
[
NH2
polyamic acid
(amidatoin) soluble
O
O
C
C
N
N
C
C
O
O
]
n
poly(pyromellitimido,-1,4 phenylene)
insoluble
Hanyang Univ.
Spring 2007
Example of condensation polymerization
Two step polymerization is used because precipitation is occured before high molecular
aromatic polyimide was formed.
• In first step, poly(amic acid) is formed at -70 oC
• The poly(amic acid) is cyclized over 150 oC.
• Aromatic polyimide is very high heat resistance, Kapton, H-film
• To improve solubility of poly(amic acid), CH2 group is introduced in aromatic amine or
isocyanate is used instead of amine.
Surfing to the internet
For further details about Polyimides
Click next homepage.
http://www.pslc.ws/mactest/imide.htm
Hanyang Univ.
Spring 2007
Example of condensation polymerization
E. Aromatic Polysulfone
O
CH3
n NaO
C
8
ONa
S
n Cl
+
CH3
DMAc
4,4'dichloro diphenyl sulfone
O
O
Cl
O
high nucleophilicity
*
-NaCl
CH3
S
O
n
*
CH3
O
polysulfone
amorphous polymer, good strength, good oxidation resistance, engineering plastic, membrane material
AMOCO PERFORMANCE Co.
UDEL.
.
Hanyang Univ.
Spring 2007
Example of condensation polymerization
F. Polybenzimidazole (PBI)
H2N
HOOC
NH2
NH2
H2N
N
COOH
-H2O
+
N
*
n
N
H
*
N
H
Hanyang Univ.
Spring 2007
Example of condensation polymerization
OH
O
C
NH2
+
C
NH C
250¡ÆC
C
NH2
NH2
_
H
N
N
H
OH
NH C
O
OH
NH2
amine, amide
-H2O 350~400¡ÆC
H
N
N
Hanyang Univ.
Spring 2007
1961 Synthesized by Marvel
Some problems :
stoichiometric problems, side reactions, oxidatio,…
Celanese Co. (http://www.celanese.com)
not burn easily, self-extinguishing, but still expensive $45/lb in 1985
Hanyang Univ.
Spring 2007
Example of condensation polymerization
G. Epoxy Prepolymers
O
CHCH2Cl
(n+2) H2C
+
CH3
HO
C
OH
CH3
(n+2) HCl
+
O
O
H2C
CH
CH2
O
O
CH2 CH
CH2
n
O
O
O
CH2 CH
OH
Structoterminal propolymer (epoxy end-group)
Hanyang Univ.
CH2
Spring 2007
Example of condensation polymerization
X-linking
O
CH CH2
OH
C
+
R
C
O
CH CH2
O
O
(f=2)
as X-linking agent
O
R
O
O
CH CH2
In this case, epoxy prepolymer is structure pendant prepolymer (OH terminated)
Hanyang Univ.
Spring 2007
Example of condensation polymerization
Curing Agnet
phthalic anhydride
maleic anhydride
O
O
O
O
O
O
pyromellitic anhydride
O
O
O
O
O
O
or
amines
Properties and Applications
Thermoset, high Chemical and solvent resistance, adhesion to many
substrates, impact resistance, structural applications
Hanyang Univ.
Spring 2007
Example of condensation polymerization
H. Unsaturated Polyesters
O
O
OH
O
OH
+
+
R
R'
OH
OH
O
O
O
R
H
O CH2 C
R'
O
CH2
O
C
O
O
alkyd resin
Hanyang Univ.
Spring 2007
Example of condensation polymerization
O
O
OH
O
+
OH
*
O
H2
C
C
H2
O
n
C
*
O
O
brittleness, softness depends on X-linking densityh.
Applications: bowling ball, helmet, auto part, air con
Hanyang Univ.
Spring 2007
Example of condensation polymerization
I. Polycarbonate
O
Cl C Cl
+
HO
OH
O
*
O
O C
n
*
+
HCl
Lexan from GE
Tm = 270°C, Tg=150°C
high impact resistance, transparency, packaging, phone dial ring,
process similar to polyester synthesis
2stage,
①vaccum at 200°C
②300°C
Hanyang Univ.
Spring 2007
Example of condensation polymerization
J. Poly urethane
+
HO(CH2)nOH
O C N
diol
diol
(CH2)6N
C O
HMDI (hexamethylene diisocyanate)
CH2
+
NCO
OCN
4,4'-diphenylmethane diisocyanate
or
diol
+
NCO
NCO
CH3
TDI (tolylene diisocyanate)
Hanyang Univ.
Spring 2007
Interfacial Polymerization
diamine in water
Polymer film forming at the interface
diacid chloride in organic solvent
O O
O O
n Cl CR C Cl
+
n HOR'OH
*
O O
n Cl CR C Cl
CR C R' O
2n HCl
n
*
+
n
*
+ 2n HCl
O O
+
n H2NR'NH2
*
H H
CR C N R'N
Hanyang Univ.
Spring 2007
Nylon-6,6
O
O
O
NaOH
Cl
4
Cl
Adipoyl chloride
H2N
4
NH2
Cl
O
N
H
4
1,6-Diaminohexane
O
Adipoyl chloride
in hexane
HO
N
H
4
O
N
H
4
4
N
H
Nylon 6,6
Diamine, NaOH, in H2O
H
6 carbon
diacid
6 carbon
diamine
Nylon-6,6
Hanyang Univ.
H
n
Spring 2007
Nylon-6,6
Since the reactants are in different
phases, they can only react at the
phase boundary. Once a layer of
polymer forms, no more reaction
occurs. Removing the polymer allows
more reaction to occur.
Adipoyl chloride
in hexane
Nylon 6,6
Diamine, NaOH, in H2O
Hanyang Univ.