1. 1. Introduction
The technology enhancement of any population is connected to the materials available.
Therefore scientists have developed new materials to cope with the development of human
civilisation. With the use of organic chemistry, new material is producing commonly
synthetic polymers. Due to the versatility of these polymers it allows creation and fabrication
of materials that cannot be attain from materials such as wood, metals and ceramics. The raw
materials of polymer derived from petroleum and with the advance technology the synthesis
of raw material became cheap and useful.
2. Step Growth or Condensation Polymerizations
Step Growth polymerization is a polymerization process in which chain growth occurs in
stepwise manner. It is formed by reaction of difunctional molecules, with each new bond
created in separate steps. Monomers will react with other monomers to form dimmers,
dimmers than react with dimer to form tetramers, tetratmer react with monomers to form
pentamers and so on. The stepwise manner plays an important role for both their molecular
weights and molecular weight distribution. At the end high molecular weight polymer
molecules is produce. The step growth process can be done in two ways; (1) reaction between
A-A monomers will react with B-B monomers to give (A-A-B-B) polymer and (2) the self
condensation A-B monomer to give (A-B)n polymers. New covalent bond is formed at the
end of polymerization by polar reaction such as nuclephilic acyl substituition.
2.1. Polyamides
Wallace M. Carothers and his associates E.I. Dupont de Numours & Company in the
1930s begin their fundamental research into the reaction of aliphatic dicarboxylic
acids and diols. From adipic acid and ethylene; a high molecular weight polymer is
obtained that could be drawn into fibres which are polyesters.
O O
HO H3C CH3
O
OH + HO
OH
O
O O
Hexanedioic acid 1,2-Ethanediol Poly(ethylene adipate)
(Adipic acid) (Ethylene glycol)

2. The polyesters fibres had melt transitions (Tm) too low for use as textile fibres. Then
he concentrates to reactions of dicarboxylic acids and diamines to form polyamides
and 1934 synthesized nylon 6, 6 is made which is a purely synthetic fibres. Nylon 6,
6 is synthesized from two different monomers, each containing six carbon atoms.
O
HO H2N
+
OH NH2
O Hexanedioic acid 1,6-Hexanediamine
(Adipic acid) (Hexamethylenediamine)
O
-O
+
O- NH 3
+NH 3
O
Nylon salt
O
-O NH
CH3
NH n
O Nylon 6,6
The conditions that is suitable to form nylon 6,6 is the Tm has to be between 250-
260C and the molecular weight is in the range of 10,000-20,000 g/mol.
The first step of fiber production, crude nylon is melted, spun into fibers and cooled.
The melt-spun fibers are cold drawn (drawn at room temperature) to about four times
their original length to increase their degree of crystallinity. Next, individual polymer
molecules become orientated in the fiber axis, and hydrogen bond form between
carbonyl oxygen of one chain and amide hydrogen of another chain. The physical
properties of the fiber from polyamide are impressive because both tensile strength
and stiffness increase due to the effects of orientation of polyamide molecules.
The existing raw material base for the production of nylon 6, 6 is benzene which
arises from catalytic cracking and reforming of petroleum. A mixture of
cyclohexanol and cyclohexanone is produce when benzene is catalyzed to
cyclohexane by catalytic reduction and then followed by catalyzed air oxidation.
Oxidation of this mixture by nitric acid will gives adipic acid.

3. O
3H 2 O2 OH O HNO 3
OH
catalyst catalyst
+
OH
benzene cyclohexane
cyclohexane cyclohexanone O
hexanedioic acid
(Adipic acid)
Adipic acid is the starting material for synthesis of hexamethylenediamine. Reaction
od adipic acida and ammonia give ammoniums salt, which when heated will give
adipiamide. If adipic acid is catalytic reduce it will give hexamethylenediamine.
Hence the formation of nylon 6, 6 are completely from petroleum which is sadly
unrenewable.
+ O
NH 4 O
O
+ H2N
O NH 4
NH2
O
O
Ammonium Hexanedioate
Hexanediamide
(Ammonium adipate) (Adipamide)
H2N
NH2
1,6-Hexanediamine
(Hexamethylenediamine)
Nylon can be categories as polymers, the members of which have tactfully different
properties that suits them to one use or another. Nylon 6,6 and nylon 6 are the most
popular polymers. Nylon 6 is so named because it is synthesized from caprolactam a
six carbon monomer. In the synthesis of nylon 6, caprolactam is partially hydrolyzed
to 6-aminohexanoic acid and then it is heated to 250C to start the polymerization.
Nylon 6 is fabricated into fibers. Brush bristle, ropes, high impact molding and tire
cords.
O
Hydrolysis O
NH
NH
Heat H CH3
n
Nylon 6
Caprolactam

4. Based on extensive research of the relationship between molecular structure and bulk
physical properties, scientist at Dupont reasoned that polyamide containing aromatic
ring will become stiffer and stronger than either nylon 6 or nylon 6, 6. From there
Kevlar where produce, a polyaromatic amide fiber synthesized from tetraphthalic
acid and p-phenylenediamine. The amazing features of Kevlar are that it is light
weighted and strong even if it is compared with other material that have the same
strength. Kevlar is used as anchor cables for offshore drilling rigs and reinforcement
fibres for automobiles tires. Because of its remarkable feature it is also woven into
fabric such as bulletproof vest, jackets and raincoats.
2.2. Polyesters
Carothers and his associates deduce that polyesters fibers are produce from aliphatic
dicarboxylic acids and ethylene glycol were not suitable for textile use because of
their low melting point. In 1930s Winfield and Dickson studied polyesters and found
that the a greater resistance to rotation of polymer backbones will stiffen the
polymer, this is done by increase its melting point which will then result of an
acceptable polyester fibres. Terephthalic acid is used to create the stiffness of
polymer chain. Polymerization of this aromatic dicarboxylic acid with ethylene
glycol will give poly(ethyleneterephthalate) or PET.
O O
O O OH
O
+ HO
H3C O CH3
HO OH n
1,2-Ethanediol
Poly(ethylene terephthalate)
1,4-Benzenedicarboxylic acid (ethylene glycol)
(Dacron,Mylar)
(terephthalic acid)
The crude polyester can be melte, extruded and then cold drawn to form tetxtile fiber
Dacron polyester. Which are four times stronger than nylon 6,6. However Dacron
polyester fibres are harsh to touch due to their stiffness hence they are mixed with
cotton or wool to make acceptable textile fibres. PET is fabricated into Mylar films
and recycle plastic beverages containers.
For the synthesis of PET; ethylene glycol is obtained by air oxidation of ethylene to
ethylene oxide followed by hydrolysis of glycol. Ethylene id obtained from cracking
either from petroleum or the ethane from natural gas. Whereas by oxidation of p-

5. xylene will produce terepthalic acid; an aromatic hydrocarbon obtained from
catalytic cracking or reforming of naptha or petroleum.
O +
H , H 2O
H2C CH2
HO OH
Phenol Oxirane 1,2-Ethanediol
(Ethylene Oxide)
CH3
O2 O O
HO OH
H3C catalyst
p-xylene
Terephthalic acid
2.3. Polyurethane
Urethane is and ester of carbamic acid H2NCOOH. Urethane is the name derived
from the functional group formed from the reaction of an isocyanate group with a
hydroxyl group.
R N
O R' OH R NH O R'
O
isocyanate
carbamate
Polyurethanes consist of a flexible polyester or polyether unit alternating with rigid
urethane units block. The rigid urethane block is derived from diisocyanate, generally
a mixture of 2,4 and 2,6 toulene diisocyanate. The flexibility of this polymer depend
on the low molecular weight (MW 1000-4000) polyesters or polyether with –OH
group at the ends of the polymer chain. Fibers forms from polyurethane are fairly soft
and elastic. It is usually used as Spandex and Lycra. By adding small amount of
water during polymerization polyurethane foams for upholstery and insulating
materials are made. This is because water react with isocyanate groups to produce
carbon dioxide gas which act as a foaming agents

6. O
O N N
HO polymer OH
+
2,6- Toulene diisocyanate Low Molecular Weight polyester or polyether
O O
CH3 O CH3
NH NH n
H3C O polymer
polyurethane
H H
O
O O O
R N O + R NH
OH
R NH2 +
isocyanate
carbamic acid (unstable)
2.4. Phenol-formaldehyde polymers
Phenol-formaldehyde polymers are thermosetting polymers composed of long chains
that are cross linked by covalent bonds. Leo Baekeland 1907 was the first to produce
thermosetting polymer. Thermosetting polymer is produce by reacting phenol with
formaldehyde to form Bakelite which is good electrical insulator.
One of the monomer must be trifunctional in their preparation of thermoset. For
Bakelite, the trifunctional monomer is phenol. Manufacture of thermosets begins
with a fluid mixture of two monomers. It is first shaped and then polymerized wither
by heating or by being mixed with an initiator. The product of polymerization is a
network of covalently bonded atoms that is solid, even at room temperature. The
thermoset polymers char and decompose at high temperature but they do not melt.

7. CH 2 CH 2
OH CH4
H4C
+ H2C O OH OH
Formaldehyde CH 2
Phenol CH4
OH
CH 2
CH 2
H4C
o
OH OH
CH 2
CH4
Bakelite
CH 2
H4C
3. Summary
 Step growth polymerization is also known as condensation step
 For step growth polymerisation, monomers should have at least two functional
group. Both functional group may be the same or different
 Monomers having two functional group always give linear polymer
 Step growth polymer do not contain all the atoms initially present in monomers
 The polymerization takes place between monomeric units with the elimination of
small molecules such as water, ammonia, alcohol etc.
 Monomers having three functional groups alway gives cross-linked polymer.
Example: urea-formaldehyde, phenol-formaldehyde resin, alkyd resin
 All resins are cross-linked polymer and all cross-linked polymers are
condensation polymers

8. Reference
 Dhawan. P, Organic Chemistry, Tata McGraw Hill Publishing Company Limited,
2008
 Lim Yo Sie, Mohd Hilmi Jaafar, William H.Brown, Christopher S. Foote, Organic
Chemistry,Thomson Learning,2006
 Mark.G.G, Wittcoff. H,Organic Chemistry, Principles and Industrial Practice,Die
Deutsche Bibliotek, 2003
 Nicholson.J.W, The Chemistry of Polymer, 3rd Edition,RSC Publishing, 2006
 Solomons G.T.W, Fryhle.B.C, Organic Chemistry, 10th Edition,John Wiley & Sons
(Asia) Pte.Ltd, 2011
 William H. Brown, Christopher S. Foote, Brent L. Iverson, Eric V. Anslyn,Organic
Chemistry,5th Edition,Brooks and Cengage Learning, 2010