Condensation Polymerisation (AQA GCSE Chemistry)

Higher tier only

• Condensation polymers are formed when two different monomers are linked together with the removal of a small molecule, usually water
• This is a key difference between condensation polymers and addition polymers:
  • Addition polymerisation forms the polymer molecule only
  • Condensation polymerisation forms the polymer molecule and one water molecule per linkage

• The monomers have two functional groups present, one on each end
• The functional groups at the ends of one monomer react with the functional group on the end of the other monomer, in so doing creating long chains of alternating monomers, forming the polymer
• Polyesters are formed from two different monomers and produce water
• For every ester linkage formed in condensation polymerisation, one molecule of water is formed from the combination of a proton (H⁺) and a hydroxyl ion (OH^–)
• An example is terylene which is a polyester made from dicarboxylic acid monomers (a carboxylic with a -COOH group at either end) and diols (an alcohol with an -OH group at either end)
• Each -COOH group reacts with another -OH group on another monomer
• An ester linkage is formed with the subsequent loss of one water molecule per link

Formation of a polyester

The condensation reaction in which the polyester terylene is produced

• The structure of terylene can be represented by drawing out the polymer using boxes to represent the carbon chains
• This can be done for all polyesters

Repeating units of terylene

Diagram showing a section of the polyester terylene