Download Polyesters are condensation polymers.

Polyesters are condensation polymers.
Esters are compounds formed from carboxylic (alkanoic) acids and alcohols (alkanols).
When they form, a molecule is lost (water in this case).
Note that sometimes other molecules (HCl for eg) are lost in other
condensation reactions.
It is the elimination of a molecule which makes it a condensation reaction,
not the loss of water.
When the carboxylic acid and alcohol react they form an ester group, –COO–.
More on this in The Acidic Environment.
Polyesters are formed by the reaction between a dicarboxylic acid and a diol.
Can you see why this would encourage a polymer to form?
Polyesters are condensation polymers. When they form, a molecule is lost
(water in this case) every time two monomers join.
The dicarboxylic acid and diol are linked by an ester group.
What happens next do you think?
Notice that there is a carboxyl group on one end of the molecule and a hydroxyl
group on the other end.
Notice that there is a carboxyl group on one end of the molecule and a hydroxyl
group on the other end.
Notice that there is a carboxyl group on one end of the molecule and a hydroxyl
group on the other end. Have you worked it out yet? Too easy?
The unreacted groups on each end can react to link together.
When this happens, a polyester forms.
Terylene is a polyester. Many monomer units are present in a single polymer chain.
An example of a condensation polymer – NOTES !!!!
teraphthalic acid
Teraphthalic acid is a dicarboxylic acid that can form a polyester with a diol.
teraphthalic acid
1,2-ethanediol
1,2-ethanediol is a diol that can form a polyester with a dicarboxylic acid.
teraphthalic acid
1,2-ethanediol
What is the repeating unit of the polyester formed if n monomer molecules react
together?
teraphthalic acid
Water is formed in the reaction.
1,2-ethanediol
teraphthalic acid
1,2-ethanediol
A polyester with this repeating unit is also formed in the reaction.
The polyester formed is polyethylene terephthalate, or PET.
teraphthalic acid
1,2-ethanediol
1 repeating unit of polyethylene terephthalate
PET is used for strong bottles (fizzy drinks) and some clothing fibres.