Polymers

• Types of polymerisation

  • Addition polymerisation
  • Condensation polymerisation
• Condensation Polymerisation

  The joining of monomers (which can be different) with the elimination of a small molecule such as water or HCl.
• The two main types of condensation polymers

  1. Polyesters
  2. Polyamides
• Condensation Polymerisation

  • If there is an ester link, the polymer is a polyester (formed by condensation polymerisation)
  • If there is an amide link, the polymer is a polyamide (formed by condensation polymerisation)

  This requires one type of monomer which has two different functional groups or two different types of monomers which have functional groups that can react together via condensation. These are known as bifunctional molecules.
• Polyesters can be made from:

  • A dicarboxylic acid and a diol (two different monomers)
  • A hydroxycarboxylic acid (one type of monomer)
• In forming a polyamide the monomers are linked together by condensation via an amide ‘link’ and water is eliminated. Polyamides can be made from:

  • A diamine and a dicarboxylic acid (two different monomers)
  • A amino acid (one type of monomer)
• Biodegradable polymers

  Both polyesters and polyamides can be broken down using hydrolysis reactions. This is a major advantage over the polymers produced using alkene monomers (polyalkenes). When polyesters and polyamides are taken to landfill sites, they can be broken down easily and their products used for other applications. Condensation polymers however are hydrolysed (slowly naturally with water) or under acidic or basic conditions in the laboratory.
• Hydrolysis of Polyesters

  Ester linkages can also be degraded through hydrolysis reactions

  • Acid hydrolysis: forms the diol and dicarboxylic acid that were used to form the polyesters
  • Alkaline hydrolysis: forms the diol and dicarboxylic acid salt