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Hanyang Univ.Hanyang Univ.
Spring 2007
Classification by Mechanism
Step – Growth
Chain – Growth
Classification by Type
Condensation
Addition
Classification by Bond
Radical
Ion
Chap 8. Polycondensation Reactions
For further details,
Click next homepage.
http://www.pslc.ws/mactest/synth.htm
Surfing to the internet
Hanyang Univ.Hanyang Univ.
Spring 2007
Step Growth Polymerization
•The growing chains react with each other.
•Polymers frwo to high Mw at a slow rate.
•High Mw is formed at the end of polymerization.
•Long reaction time is needed to obtain high Mw and high conversion
Chain Growth Polymerization
•Monomer molecules add on to a growing polymer chain one at a time.
•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.
What are differences between step and chain growth polymerizatoin?
Hanyang Univ.Hanyang Univ.
Spring 2007
Addition versus Condensation polymerisation
• Condensation polymers (C): fewer atoms in the backbone because of formation of by-products
• Addition polymers (A): the repeating unit contains the same atoms as the monomer
OH OH
O O
2NH2 NH2
6 * N N *
O O
H Hn
4 6+
**
OO
n
**
n
OO
Hanyang Univ.Hanyang Univ.
Spring 2007Characteristics of Step-Growth
Step-growth polymerization principle was used by Carothers in 1929.
HO C
O
CH2CH3OH CH2CH3 CH3 CH2 C
O
O CH2CH3
Synthesis of Ester
Carothers thought about following reaction.
OH C
O
R C
O
OH R' OHOHMany scientists were sure that one would get a ring-like moleculeO
R'O
RO O
But, if more acid and alcohol were used, ring would not form because of unstability of ring-shaped molecules more than six atom.
It seemed to him more likely that one would get long chainlike macromolecules like this
Hanyang Univ.Hanyang Univ.
Spring 2007
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”
Characteristics of Step-Growth
OH C
O
R C
O
OH R' OHOH
Hanyang Univ.Hanyang Univ.
Spring 2007
Extended by Flory
The reactivity of functional group is not correlated with complexity and size of molecule with
functional group.
HO R OH + HOOC R' COOH (complexity)
HO R OH (size)
HO R OH
This concept is useful to polycondensation type polymerization.
ex) OCNRNCO + H2NR`NH2 polyurea
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
This concept also can be applied to Chain-growth polymerization.
Olefins
Vinyl monomers
Unsaturated monomers
So, double bond in vinyl monomer is considered as bifunctional.
Equal Functional Group Reactivity Concept
C C
H
H
H
H
C C OR
H
H
H
H
OR C C OR
H
H
H
H
CCC
H
H
H
H
H
H
C C
H
H
H
H
Hanyang Univ.Hanyang Univ.
Spring 2007
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 = HTS
GP = HPTSP : this equation is the basic of understanding about polymerization,
depolymerzation equilibrium
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
GP = Gpolymer Gmonomer
= (HP – Hm) – T(SP – Sm)
= HP – TSP
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)
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
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.
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
Stage 1
Consumptionof monomer
n n
Stage 2
Combinationof small fragments
Stage 3
Reaction of oligomers to give high molecular weight polymer
Step Growth Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
1. Polyesterification by esterinterchange
2. Polyesterification and polyamidation by Schotten-Baumann Reaction
O
C Cl+
NH2
OH
O
x
OO
R" (OCR' C O R ) OH + (2 x 1)R" OH
O
x HO R OH + xR"OCR' C O R"
Step Growth Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
3. Amidation by thermal dehydration of ammonium salt
4. Reaction of OCNRNCO + HOR’OH polyurethane
H2NR’NH2 polyurea
n46H NH (CH2) NH CO (CH2) CO OH + (2n 1) H2O
++
6 H3N(CH2) NH3
4OOC(CH2) COO
n
46n H2N(CH2) NH2 + n HOOC(CH2) COOH
Step Growth Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
Well-studied, well characterized rexns
Well-understood rexns at least on an empirical basis.
X-linked, inefficient rexn.
OHOH
CH2CH2
CH2 OO CH2
polyfunctional
high MW, linear?CH2O+
OH
Step Growth Polymerization
For further details,
Click next homepage.
http://www.chemheritage.org/EducationalServices/nylon/other/step/step.html
Surfing to the internet
Hanyang Univ.Hanyang Univ.
Spring 2007
W. Carothers
In step-growth polymerization, Carother's equation gives the number-average degree of
polymerization, Xn, for a given fractional monomer conversion, p.
eq. sCarother'P1
1DP
P1
1
M
M
N
NDP
P1MM
n
00n
0
P = extent of reaction
[M]= concentaration of monomer
Carother’s Equation
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.Hanyang Univ.
Spring 2007
2f ifP1
1
fP2
2DP
fDP
2
f
2P
)2( )1(eqn From
)2(N
N
reactionafter molecules of moles ofNumber
monomers ofnumber InitialDP
)1(fN
)NN(2
initially groups functional ofNumber
used groups funtional ofnumber The P
n
n
0n
0
0
Generalized Carother's Eq.
Carother’s Equation
f = number of average functional group per monomer
N0 = number of initial monomers
N0f = number of initial functional group
N = number of final molecules (monomer, dimer, polymer)
Hanyang Univ.Hanyang Univ.
Spring 2007
ex) monomer=10, fg= 20
final molecules= 2
R.O) then R.US.U (if S.U ofnumber is DP
58.01
1DP
8.010
8
102
2)-2(10P
n
n
Carother’s Equation
For further details about W.Carothers
Click next homepage.
http://www.chemheritage.org/EducationalServices/chemach/pop/whc.html
Surfing to the internet
Hanyang Univ.Hanyang Univ.
Spring 2007
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)
OH (CH2)5COOH
-CO2
OH (CH2)4CH3 + CO2
High monomer purity
Exact (on known) Stoichiometry
Four Requirements of Polycondensation
Exact (on known) equivalence of functional groups.
Molecular Weight Control of Polycondensation Reaction
Equivalence of Functional Groups.
Hanyang Univ.Hanyang Univ.
Spring 2007
A. Types of monomer
a. AB type
HO COOH
b. AA and BB type
HOOC COOH HOCH2CH2OH
c. Three functional groups for crosslinked polymers
HOCH2CHCH2OH
OH
Kinetics (ref. chap 11 in book)
Hanyang Univ.Hanyang Univ.
Spring 2007
B. Condensation of difunctional monomers. a.
b.
HOCH2CH2OHH+
(-H2O)* OCH2CH2 *
O
O
H2NCH2CH2CH2CO2H∆
(-H2O)
NH
O
* NHCH2CH2CH2C *
O
Kinetics (ref. chap 11 in book)
Hanyang Univ.Hanyang Univ.
Spring 2007Kinetics (ref. chap 11 in book)
Polyesterfication as an example of polycondensation
- 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
COOH OH CO
O
Hanyang Univ.Hanyang Univ.
Spring 2007
- 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
Kinetics (ref. chap 11 in book)
[COOH] = [COOH]0 (1-P)
PDPn
1
1tk [COOH] 1 20nDP
If you know the value of K2, you can calculate DPn at any time
Assumption : with strong acid catalyst condition, pure monomer and correct equivalent
Hanyang Univ.Hanyang Univ.
Spring 2007Kinetics (ref. chap 11 in book)
ex)k 2 10 –2 l mole1sec1 , C0 3 mole sec l1 , DPn =50( k2 = kcat[H+] )
Reaction time = ?
if k 2 10 –4 l mole1sec1
Reaction time = ?
less than 30 min
about 45 hr
Hanyang Univ.Hanyang Univ.
Spring 2007
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 x1
Probability finding a unreacted carboxyl group in molecules = 1P
Probability finding x-mer = P x1(1-P)
Kinetics
Mw distributions of linear condensation polymers
Hanyang Univ.Hanyang Univ.
Spring 2007
If there are N number of molecules, total x-mer number is
N x = N P x1(1-P)
N = N 0 (1 P)
N x = N 0 P x1(1P) 2
Mw distributions of linear condensation polymers .
0.045
0.010
0.020
P=0.95
P=0.98
P=0.99
Nx
100 220
Kinetics
Hanyang Univ.Hanyang Univ.
Spring 2007
xNxnDP
1-x2
0
p)p1(
xN
NxW x
x
PnDP
wDP
p
p
WxxwDP
xw
1
79 pageodian 1
1
2.0MWD
4
213
312
21
)1(
41
)1(
1
)1(
1
P
PPpx
P
Ppx
Pxp
x
x
x
Kinetics
Hanyang Univ.Hanyang Univ.
Spring 2007
Target Molecular weight
DPn is time – dependent
1) Quench (cooling) the polymerization at pre- determined time
heating unstable
HO R COOH HO COOH
HOOC OH
react as heating undesirable
Molecular Weight Control
Hanyang Univ.Hanyang Univ.
Spring 2007
2) Regulation of monomer concentration
nonstoichiometric condition or adding monofunctional reactant.
HO R OH HOOC COOH
HOOC COOH
+ HOOC R' COOH
EXCESS
• Stable Polymer
• No more reaction.
can control & limit MW
Molecular Weight Control
Hanyang Univ.Hanyang Univ.
Spring 2007
Nylon 66: Adding lauric acid or acetic acid, MW control
Possible melt spinning through viscosity control
melt viscosity
mw
undesirable
Molecular Weight Control
Hanyang Univ.Hanyang Univ.
Spring 2007
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) / 2Number 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
Molecular Weight Control
Hanyang Univ.Hanyang Univ.
Spring 2007
A. Greater than two functionality polymers. a. Alkyd-type polyester :
b. Phenol-formaldehyde resin :
c. Melamine-formaldehyde resin :
HOCH2CHCH2OH
OH
OH
N
N
N
NH2
H2N NH2
Network Step Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
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.
Network Step Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
C. Gel point conversion.
: critical reaction conversion. : average functionality.
rrpc
[
1
avf
cp
avc f
p2
o
o
N
NNp
Network Step Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
4.25
)32()23(
avf
D. Examples of gel point conversion.
O
O
O
HOCH2CHCH2OH
OH
3mol of 1 2mol of 4
Gel point conversion : 77% (Experiment)
83% (Calculate)
Network Step Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
DPn ∞
i
ii
N
fNavgf
Ni:Monomer have functional group, f i
ex) 2mole Glycerol 6OH
3mole Phthalic Acid 6COOH
total 5 mole 12 f.g
N, No , No favg=total functional group
2( No- N) = number of functional
group after reaction
avg
avg
pfN
NDPn
fN
NNP
2
2
)(2
0
0
0
Carother’s Equation
4.25
12avgf
where DPn ∝
= critical extent of reaction at gel point
In case of ex.
Pc = 2/2.4 = 0.833
avgc f
p2
Hanyang Univ.Hanyang Univ.
Spring 2007
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.
Example of condensation polymerization
For further details about Polyester
Click next homepage.
http://www.pslc.ws/mactest/pet.htm
Surfing to the internet
Hanyang Univ.Hanyang Univ.
Spring 2007
CH3OC COCH3 + HO(CH2)2OH2
O
HOCH2CH2OC COCH2CH2OH
O
O O
+CH3OH2
1.
2. O
HOCH2CH2OC COCH2CH2OH
O
n
O O
COCH2CH2OHOCH2CH2O-C H + HOCH2CH2OH(n-1)
n
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
. nylon salt
NH2 (CH2)6 NH2n + HOOC(CH2)4COOHn n O2C(CH2)4CO2
H3N(CH2)6NH3
- -
+
H NH
(CH2)6 NH
C (CH2)4 C
O
OH
O
+ OH2(2n-1)
B. Nylon 66
For further details about Nylon
Click next homepage.
http://www.pslc.ws/mactest/nysyn.htm
http://www.pslc.ws/mactest/nylon.htm
Surfing to the internet
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
Kevlar poly(p-phenylene terephthalamide) -high strength
NH2 NH2
HN NHC
O O
n
HOOC COOH+
C
C. Aromatic Polyamide
For further details about Kevlar and Nomex
Click next homepage.
http://www.pslc.ws/mactest/aramid.htm
Surfing to the internet
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
Nomex poly(m-phenylene isophthalamide) -very good high temperature resistance
+NH2 NH2
HOOC COOH -HCl-H2O
CH2Cl2DMAc
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.
Li C O
C
O
Example of condensation polymerization
* Coordinated covalent bond by using Li ion
Hanyang Univ.Hanyang Univ.
Spring 2007
O
OO
O
O
O
O
O
+ NH2NH2
DMAcDMFDMSO
Pyromellitic dianhydride p-aminoaniline
(PMDA)
HOOC COOH
O
CNH NH
[ ]n
-H2O
O
C
O
C
CC
N
O
N[ ]n
polyamic acid(amidatoin) soluble
poly(pyromellitimido,-1,4 phenylene)
insoluble
nn
D. Aromatic Polyimides
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
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.
For further details about Polyimides
Click next homepage.
http://www.pslc.ws/mactest/imide.htm
Surfing to the internet
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
NaO C8
CH3
CH3
ONa Cl
O
O
S Cl
-NaCl
O* O
CH3
CH3
*n S
O
O
+ DMAc
4,4'dichloro diphenyl sulfonehigh nucleophilicity
polysulfone
n n
amorphous polymer, good strength, good oxidation resistance, engineering plastic, membrane material
E. Aromatic Polysulfone
AMOCO PERFORMANCE Co. UDEL.
.
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
NH2
NH2
NH2
NH2
HOOC COOH-H2O
N
NH
N
NH
* *n
+
F. Polybenzimidazole (PBI)
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
NH2
NH2
+
O
250¡ÆC
OH_
O
amine, amide
-H2O 350~400¡ÆC
NH
N
NH
NH
OH
NH
NH2
C
NH
NH2
C
OH
CC
C
Example of condensation polymerization
Hanyang Univ.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.Hanyang Univ.
Spring 2007
CH2
OCHCH2Cl +
ClH +
CH2
O
CH CH2 O O CH2 CH
OH
CH2 On
O
O O CH2 CH CH2
OH C
CH3
CH3
OH
(n+2)
(n+2)
Structoterminal propolymer (epoxy end-group)
G. Epoxy Prepolymers
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
X-linking
CH
OH
CH2 + RC
CO
O
O
CH CH2
O
O
R
O
O
CH CH2
(f=2) as X-linking agent
In this case, epoxy prepolymer is structure pendant prepolymer (OH terminated)
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
phthalic anhydrideO
O
O
maleic anhydrideO
O
O
pyromellitic anhydride
O
O
O
O
O
O
Curing Agnet
Example of condensation polymerization
or
amines
Properties and Applications
Thermoset, high Chemical and solvent resistance, adhesion to many
substrates, impact resistance, structural applications
Hanyang Univ.Hanyang Univ.
Spring 2007
O
O
O +
OH
OH
OH+ R
R'
O
OH
RR'
OO CH2 C
H CH2O
C
O
O
O
O
alkyd resin
H. Unsaturated Polyesters
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
O
O
O +OH
OH OCH2
CH2
OC
O
*
O
* n
brittleness, softness depends on X-linking densityh.
Applications: bowling ball, helmet, auto part, air con
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
C
O
ClCl+ OH OH
O* O C
O
*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
I. Polycarbonate
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
HO(CH2)nOH O C N (CH2)6N C O
OCN
CH2 NCO
NCO
NCO
CH3
+
diol HMDI (hexamethylene diisocyanate)
diol
+
4,4'-diphenylmethane diisocyanate
or
+
TDI (tolylene diisocyanate)
diol
J. Poly urethane
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
diamine in water
Polymer film forming at the interface
diacid chloride in organic solvent
O
CR C
O
ClCl + HOR'OHnn
O
CR C
O
R'O ** n + 2n ClH
O
CR C
O
ClCl + H2NR'NH2nn
O
CR C
O
* N R'NH H
*n 2n ClH+
Interfacial Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
Cl Cl
O O
4H2N NH24
Adipoyl chloride 1,6-Diaminohexane
Cl NH
NH
H
O O
4 4
NaOH
HO NH
NH
H
O O
4 4n
6 carbondiacid
6 carbondiamine
Nylon-6,6Diamine, NaOH, in H2O
Adipoyl chloridein hexane
Nylon 6,6
Nylon-6,6
Hanyang Univ.Hanyang Univ.
Spring 2007
Diamine, NaOH, in H2O
Adipoyl chloridein hexane
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.
Nylon-6,6