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Module 6
Condensation polymers
Polymers such as polyesters are formed by elimination reactions, when monomers join together and
release a small molecule such as water.
Polyesters
Polyamides
Polyesters are condensation polymers, normally
formed when a dicarboxylic acid reacts with a diol,
to form a polymer and water.
PET, used in plastic bottles, is an example:
Polyamides are condensation polymers, normally
formed when a dicarboxylic acid reacts with a
diamine, to form a polymer and water.
Nylon-6,6, used in synthetic rope, is an example:
O
O
n C
C + O
H
CH2CH2
OH
O
O
C
C
O CH2CH2
PET
C
n
OHH ethane-1,2-diol
OH
benzene-1,4-dicarboxylic acid
H
(CH2)6
N
+
1,6-diaminohexane
H
N
n
O
O
(CH2)4
H HO
H
O
O
(CH2)6
H
O
N
C
CH
hexane-1,4-dioc acid
O
(CH2)4
C
n
Nylon-6,6
Hydrolysis of polymers
Condensation polymers can be
broken down by the reaction with
water – hydrolysis. This can be
done under both acidic and basic
conditions. In polyesters the
ester link breaks; in polyamides
the amide link breaks. The
diagram on the right shows the
hydrolysis of PET.
Under basic conditions, the salt
of the acid is formed. When
polyamides are hydrolysed under
acidic conditions the amine
groups form a salt.
O
O
C
C
O H
C
(CH2)6 C N
O
n
Acid hydrolysis heat, HCl(aq)
O
Base hydrolysis heat, NaOH(aq)
C
C
HO
O
O
O
+
C
C
+Na–O
OH
+
O–Na+
benzene-1,4-dicarboxylic acid
+
HO CH2CH2
OH
disodium benzene-1,4-dicarboxylate
+
HO CH2CH3 OH
ethane-1,2-diol
ethane-1,2-diol
H
CH2
CH2CH2
PET
Draw the products formed when the polymer Qiana
undergoes acidic hydrolysis using HCl(aq). (2 marks)
O
O
C
O
C
(CH2)6
O
H
C
N
H
CH2
This bond breaks
so the products formed are HOOC(CH2)6COOH and
N
n
–Cl+H N
3
CH2
N
n
NH3+Cl–
Draw the formula of the repeat unit of the condensation polymer formed from glycolic acid, CH2(OH)COOH.
(1 mark)
134