Amines are organic compounds which contain the
-CO2H functional group. Carboxylic acids contain the
-CO2H functional group. An amine group reacts with a
carboxyl group to produce an amide group -CONH-. A
molecule of water is eliminated. These are called condensation
reactions.
Diamines and dicarboxylic acids which contain
reactive groups in two places in their molecules can be linked
together to form a chain. Polymers made where the monomer units
are linked together by amide groups are made by a process called
condensation polymerisation.
Nylon is an example of this which can be
made from:
| H2NCH2CH2CH2CH2CH2CH2NH2 |
1,6-diaminohexane |
| HO2CCH2CH2CH2CH2CO2H |
hexanedioic acid |
These polymers are called polyamides or
nylons.
Usually the acid chloride derivative of a
carboxylic acid is used rather than the carboxylic acid because it
is a faster reaction, e.g.
|
n H2N(CH2)6NH2 |
+ |
n ClCO(CH2)8COCl |
 |
-[NH(CH2)6-NH-CO-(CH2)8CO]-n |
+ |
2nHCl |
|
1,6-diaminohexane |
+ |
decanedioyl chloride |
|
nylon-6,10 |
|
[The first digit refers to the number of carbon
atoms in the diamine, the second digit to the number of carbon
atoms in acid].
Polyesters are condensation polymers
made from dicarboxylic acids and diols (they have the OH
group at each end of the molecule).
Nylon has found many uses in engineering
because of its strength, toughness, rigidity and abrasion
resistance. This is due to the strong intermolecular forces
between the polymer chains. Due to the presence of the N-H and
C=O groups in the chains, hydrogen bonding and permanent dipole -
permanent dipole attractions are possible between the chains. In
polyethene the much weaker instantaneous dipole-induced dipole
attractions are only present, hence polythene is a much weaker
polymer.
.
