Synthetic and naturally occuring polymers

• Addition polymerisation:

  • Alkenes can be used to make polymers such as poly(ethene) and poly(propene) by addition polymerisation
  • Many small molecules (monomers) join together to create very large molecules (polymers)
  • The repeat unit has the same atoms as the monomer because no other molecule is formed in the reaction
  • When drawing out a polymer, remember to draw the bonds coming off the C's outside the brackets and the little 'n' (means there are large numbers of these molecules joined together)
• Condensation polymerisation:

  • Involves monomers with two functional groups
  • When they react, they join together, usually losing small molecules such as water, and the reactions are called condensation reactions
  • Simplest polymers are produced from two different monomers with two of the same functional groups on each monomer
  • Example: polyester has 1 monomer with 2 carboxylic acid functional groups and 1 monomer with 2 alcohol functional groups
• Amino acids:

  • Have two different functional groups in a molecule (an amine group and a carboxylic acid group)
  • React by condensation polymerisation to produce polypeptides (works the same as the polyester above just has different functional groups)
  • Different amino acids can be combined in the same chain to produce proteins
• DNA (deoxyribonucleic acid) and other naturally occurring polymers:

  • DNA is a large molecule essential for life, it encodes genetic instructions for the development and functioning of living organisms and viruses
  • Most molecules are two polymer chains, made from four different monomers called nucleotides, in the form of a double helix
  • Other naturally occurring polymers important for life include proteins (monomer= amino acid), starch (monomer= glucose), and cellulose (monomer= glucose)