Polyester

Polyester and polyamides used as fibres in clothing.
 Polyesters: To form polyester, monomers joined together by ester linkages in a long chain.
Polyesters can be made from one monomer OR two monomers…
 When a polymer made from one monomer. The OH and COOH must be next to each other or it
won’t work.
 1) Polyester Made from One Monomer:
– One monomer containing both carboxyl and hydroxyl group.
– Carboxylic acid in one molecule reacts with alcohol in another molecule to form ester
linkage and water in a condensation reaction. Ester linkage between O=C-O.
– O at one end of repeat unit C=O at other end of repeat unit.

Biodegradable Polymers:
– Monomer lactic acid forms poly(lactic acid) PLA. Lactic acid derived from maize, so more
sustainable than polymers derived from fossil fuels. Used for food packaging.
– Another example poly(glycolic) acid PGA. Both are biodegradable polymers. Isolated from
cane sugar. Used in self dissolving surgical stiches.
 Biodegradable polymers better for environment- ester/ amide links able to hydrolyse since a
polyester/ polyamide. PLA photodegradable and C=O bond absorbs UV light. Unlike hydrocarbon
based polymers.
 2) Polymers Made from Two Monomer:
– One monomer is a dicarboxylic acid with two carboxylic acid and the other monomer is diol
containing two alcohol groups.
– Double O either side of carboxylic acid and single O either side of alcohol is one repeat unit.
In the middle is ester bond.
 Diacyl Chloride: A polyester can be made with diacyl chloride instead of dicarboxylic acid,
however HCl is lost instead of water.