Chapter 4. Condensation Polymerization

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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)


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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.


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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


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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


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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.


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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


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NH2

NH2

NH2

NH2

HOOC COOH-H2O

N

NH

N

NH

* *n

+

Polybenzimidazole (PBI)


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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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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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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

Documents

Chapter 4. Condensation Polymerization