chapter 4. condensation polymerization
TRANSCRIPT
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Condensation
or
Step-Growth
Polymerization
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Classification by Mechanism
Step – Growth
Chain – Growth
Classification by Type
Condensation
Addition
Classification by Bond
Radical
Ion
Polycondensation Reactions
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Step Growth Polymerization
• The growing chains react with each other.• Polymers grow 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?
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Characteristics of Step-Growth
Step-growth polymerization principle was used by Carothers in 1929.
HO C
O
CH2CH3
OH CH2CH3 CH3 CH2 C
O
O CH2CH3
Synthesis of Ester
Carothers thought about following reaction.
It seemed to him likely that one would get long chainlike macromolecules like this
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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
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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
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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
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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)
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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
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Common types of Condensation polymers
1. Polyesters
2. Polycarbonates
3. Polyurethanes
4. Polyamides
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1. Polyesters
Fundamentals of Esterification
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• Polymer formation begins with one diester molecule reacting with one dialcohol molecule to eliminate the methanol molecule and form an ester.
• The product of ester unit has an alcohol on one
end and ester on the other, which are available for further reactions.
• The eventual result is a polyester called poly(ethylene terephthalate) or more commonly, PET.
Linear Polymers: Polyesters
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Linear Polymers: Polyesters
Made by the transesterification of the methyl ester
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Diphenol + Diacid
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Polyester Films: Properties & Products
• strong, tough, brilliant and clear
• ease of converting
• excellent temperature resistance
• strong tear-initiation and puncture resistance
• excellent oil, grease, or moisture resistance
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Polyester Films: Properties & Products
• excellent chemical resistance
• office supplies
(e.g. book jackets, carbon ribbons)
• solar film
• microfilm jackets
• laminates
• food packaging
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2. Polycarbonates
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2. Polycarbonates
• polyesters of carbonic acid (fictive compound)
• derivatives of carbonic acid are commercially available:
– phosgene
– urea
– carbonates
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2. Polycarbonates
• Esters of carbonic acid.
• Carbonic acid is in equilibrium with CO2 and water, but esters are stable.
• React phosgene with bisphenol A to obtain Lexan® for bulletproof windows.
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2. Polycarbonates
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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
2 stage,
①vacum at 200°C
②300°C
I. Polycarbonate
Example of condensation polymerization
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Polycarbonate Resin: properties & products
• one of the most versatile engineering plastics
• 200 times impact resistance of glass• long-term durability• optical clarity• corrective eyewear and sunwear lenses• CD and DVD• automotive windows
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3. Polyurethanes
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3. Polyurethanes (polycarbamates)Formation
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3.1 PolyurethanePolyurethanes (polycarbamates) Formation
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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
Polyurethane
Example of condensation polymerization
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Polyurethane foam applications
Flexible foam:
• insulators
• automobile crash panels
• bedding
• carpet underlays
• synthetic sponges
Rigid foam:
• lightweight furniture
• construction panels
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4. Polyamides
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4. Polyamides Formation
Basic Amide Chemistry
• Acid chlorides react with ammonia and amines to give amides.
• A base (NaOH or pyridine) is added to remove HCl by-product.
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Kevlar poly(p-phenylene terephthalamide) -high strength
NH2 NH2
HN NHC
O O
n
HOOC COOH+
C
Aromatic Polyamide
Example of condensation polymerization
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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.
Example of condensation polymerization
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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
Aromatic Polyimides
Example of condensation polymerization
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NH2
NH2
NH2
NH2
HOOC COOH-H2O
N
NH
N
NH
* *n
+
Polybenzimidazole (PBI)
Example of condensation polymerization
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4 Properties & Products
• extreme high tenacity
• high heat resistance
• high impact resistance
• low weight
• high chemical resistance
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Properties & Products
• vehicles
• tires
• protective clothing
• impact-resistant materials
• asbestos replacement
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Some Example of Condensation
Reactions
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Types of Condensation Reactions
1. Polyesters
OOO
R OHHO +
OOORHO OH
OOOR O **
-n H2O
n
O
O
(CH2)5HO C
O
OH (CH2)5 C
O
O
H2O
trace
-n H2O
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Types of Condensation Reactions
R NH2H2N R'OHHO
O O+
- n H2OR
HN R' N
H
O O
* *n
R NH2H2N R'ClCl
O O+
- n HClR
HN R' N
H
O O
* *n
2. Polyamides
NH
O
(CH2)5H2N C
O
OH (CH2)5 C
O
NH
H2O
trace
-n H2O
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Polyamides via Condensation -- Nylon 66
C-(CH2)4-C
OO
OOH
H
CH2-(CH2)4
-CH2 NH2NH2
+
slight excess
C-(CH2)4-C
OO
O- O-
(CH2)4
CH2 CH2
NH3+ NH3
+
Nylon Salt
60% Slurry
200 C, 15 Atm. 1 hr
NH3+(CH2)6
-NH-C-(CH2)4-C-NH-(CH2)6
-NH-C-(CH2)4-C
O
OO
OO-
8-10
270-300 C, 1hr
- H2O
NH-(CH2)6-NH-C-(CH2)4
-C
O
O
Nylon 6 6
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Types of Condensation Polymers
R O C R' C On
O
Rn
O
R' C On
O
C
O
O
O
O n
Polyesters
Polycarbonates
Polyanhydrides
O O
Rn
Polyacetals
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Lexan Polycarbonate
CH3 CH3
OO --
Na+ Na++ Cl-C-Cl
O
Aq NaOH
CHCl2
CH3 CH3
OC
O
O
+ NaCl
xLexan
Interfacial Process
Ester Interchange
OC
O
O
+
CH3 CH3
OOH
H
1) 200 C/20mm
2) 300 C. <1mm
Lexan +
OH
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Types of Condensation Polymers
RHN R' N
HO
O
C
O
O
CH3
CH3
O
R
O O
SO O
Ar
polyurethanes polyphenylene oxide
polyarylenes polyarylene ether sulfones
04/08/23 47
Low Temperature Condensation Polymerization
Interfacial or Solution in Polar Aprotic Solvents
Parameter Low Temp High Temp
Intermediates
Purity
Stoichiometry
Heat Stability
Structure
Cost
Moderate
Not Essential
Not Essential
Highly Reactive
High
High
Essential
Essential
Thermally stable
Moderate
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Interfacial or Solution Polymerization in Polar Aprotic Solvents (Con’t)
Conditions Low Temp High Temp
Time
Temperature
Pressure
Yield
By-products
Solvents
Minutes to hours
0 – 150 CAtmospheric
Low to moderate
Salts
Required
Hours to days
>250 CHigh to vacuum
Quantitative
Volatiles
None
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Applications of Low Temperature Condensations
Prep. of Infusible Thermally Stable Polymers
Prep. of Thermally Unstable Polymers
Prep. of Polymers Containing Functional Groups with Differing Reactivity
Formation of Block or Ordered Polymers(No equilibration of polymer in melt allowed)
Direct Production of Polymer Solutions for Coatings, Spinning into Fibers, Solvent Blending to form Composites
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Types of Condensation Polymers
RHN C R' C N
H
O O
NN
O
O
O
O
N
OO
N
Ar
N
SS
N
Ar
polyamides polyimides
polybenzoxazoles polybenzthiazoles
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Aromatic Polyamides “Aramids”
NH2
NH2
+
C-Cl
C-Cl
O
O
SO O
DMF, LiCl
C-NH
C-NH
NH-C
C-NH
NH-CO
O
OO
O
Can be Dry Spun to FiberAs Spun: Elongation, 23-34%,Tenacity, 4.6-5.3 g/Denier
70% Strength Retained in Ionizing Radiation
Nomex M.p. > 350 C
Unique solvent combination
M-isomers favor formation of soluble polymers