6.2.3 (a) Forming Polyester and Polyamides

(a) Condensation polymerisation to form:

(i) Polyesters

(ii) Polyamides formation from Carboxylic acids/dicarboxylic acids (or respective Acyl Chlorides) and from Alcohols/diols or Amines/diamines.

{Learners will not be expected to recall the structures of synthetic polyesters and polyamides or their monomers.}

Addition polymers are covered at GCSE.

There's really nothing added at A level, it still involves only 1 monomer which is always an Alkene.

There is only one product (the polymer) which is usually shown as the repeat unit.

The repeat unit is never longer than 2 Carbons, although there may be Carbon atoms in the side-groups (W,X,Y Z)

Condensation polymers aren't much mentioned at GCSE.

They generally involve 2 different momomers and make the polymer and another, small molecule which is often water (hence the name condensation)

The monomers (or monomer) must have two different functional groups.

Hopefully, you'll recall that making an ester requires a Carboxylic Acid, an and an Acid catalyst.

If we started with a diol (a molecule with two alcohol groups HO-R-OH instead of a normal alcohol ROH), and reacted it with a dicarboxylic acid (HOOC-R-COOH) then the esterification could happen at either end of the molecule forming a long molecule containing multiple ester linkages.

The example below makes Terrylene (you don't need to memorise it).

You must be careful not to include too many Oxygen atoms when drawing the repeat unit.

It is possible to have a single molecule that has a carboxylic acid group and an alcohol group.

For example, Lactic Acid

In this case only one monomer is needed to make a polyester.

For example, polylactic acid.

Hopefully, you'll recall that making an Amide requires a Carboxylic Acid and an Amine.

If we started with a diol (a molecule with two alcohol groups HO-R-OH instead of a normal alcohol ROH), and reacted it with a diamine (H₂N-R-NH₂) then an amide linkage could format either end of the molecule forming a long molecule.

The example below makes Nylon 6,6 (again, you don't need to memorise it).

You could do exactly the same using a diacyl chloride instead of a dicarboxylic acid, the reaction would be ab it faster but HCl would be made instead of water.