Condensation Polymerisation:
Condensation Polymerisation:
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.
