Polymers are macromolecules that consist of building blocks called monomers.
There are two methods by which polymers are made:
- Addition polymerisation
- Condensation polymerisation
In addition polymerisation, alkenes add to themselves. As this addition proceeds further a long molecular chain is formed. The alkene is the repeating unit in the chain (the monomer). The chain itself is the polymer.
If ethene is allowed to add to itself by the breaking open of the double bond, the polymer polyethene is formed.
In condensation polymerisation the addition of two monomers releases a small molecule, usually water.
In the formation of Polyester the two monomers used are ethane-1,2-diol and benzene-1,4-dicarboxylic acid. When these add, an ester link is formed and water is released:
Proteins and polypeptides are to be found in living organisms. Polypeptides are formed by a condensation polymerisation reaction between two amino acids. These two amino acids join by a peptide link and release a water molecule.
Polypeptides and proteins consist of long chains of amino acids.
Hydrolysis of a protein involves breaking the peptide link by a reaction with water.