Properties and uses of condensation polymers

Polyester and polyamides are known collectively as condensation polymersbecause they are formed by a condensation reaction.

Condensation polymers are generally formed from straight chains which consist offew branches. This is due to the fact that they are created by reactions withheterolytic mechanisms as opposed to homolytic mechanisms (which are more random). On the other hand, addition polymers are created through free radical addition mechanisms which form a variety of products and, therefore, morebranching.

The lack of branching means that condensation polymers tend to be linear and the chains are able to pack closely together. Therefore, these polymers are more rigidand have a higher tensile strength than addition polymers. Polyamides also containhydrogen bonding which increases their strength further. Those that occur naturallycan even contain intramolecular hydrogen bonding which causes the molecule to curl up into a helical structure.

Both polyamides and polyesters are used popularly in high-strength synthetic fibres:

Polyesters are used to substitute wool and cotton in clothing, carpets and rugs. They are also present in bullet-proof vests and some forms of fire-resistant clothing.
Polyamides have more elastic properties and are used in items like fishing nets and underwear as well as other synthetic fibres.

Possibly the most important difference between condensation and addition polymers is that the former is composed of chains which contain polar bonds. In other words, the polymer units are linked with C-N and C-O bonds. As nucleophiles can readily attack these polar carbon atoms, condensation polymers can be readily broken up and themonomers reformed. This means that they are biodegradable making them much less of an environmental hazard than addition polymers.

Condensation polymers can be broken up in aqueous solution, a reaction which is classed as a hydrolysis reaction.

Polyesters hydrolyse best in strongly alkaline conditions. Here they undergosaponification.
Polyamides hydrolyse best in strongly acid conditions.

However, their biodegradability means that they are less durable. It is important, therefore, that a balance is struck between practical durability and biodegradability.

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A simple note explaining Polymers and how they react and change. All this is from the A-Level Chemistry course. Credit to: www.getting-in.com/

A-Level Chemistry: Polymers