23. Macromolecules

Macromolecules

• Macromolecules are very large molecules made by joining thousands of identical small molecules called monomers. 
• The process of chemically joining up the monomers is called polymerization. 
• The very large molecule formed is called the polymer.

Addition Polymerisation

• An addition polymer is formed when unsaturated monomers, containing C=C bonds, joined up to form a polymer without any loss of atoms.
  
• The C=C bonds become C-C single bonds in the process.
  

Condensation Polymerisation

• Condensation polymers are made from monomers containing alcohol, acid or amino (-NH2) functional groups.
  
• At least 2 types of monomers are alternately chemically joined together, in a condensation reaction, to form a large molecule. 
  
• In the condensation reaction, for every linkage formed, a small molecule, such as water, is removed.
  

Nylon - a Polyamide

• Nylon is made from condensation polymerisation.
  
• Diamine molecules and dicarboxylic acid molecules react together.
  
• Water molecules are removed in the process.
  
• An amide linkage is formed. -CONH-
  
• Nylon is used to make ropes, fishing lines, clothes, tents and parachutes.
  
  

Terylene - a Polyester

• Terylene is made from condensation polymerisation.
  
• Diol molecules and dicarboxylic acid molecules react together.
  
• Water molecules are removed in the process.
  
• An ester linkage is formed. -COO-
  
• Terylene is made into fibres which are woven into cloth which do not wrinkle easily.
  

Pollution Problem caused by Plastics

• Plastics are non-biodegradable, which means that they are not broken down easily into simpler substances by microorganisms like bacteria and fungi in soil.
  
• When burnt, they produce toxic gases like CO and HCl which pollute the air.
  
• When discarded, plastics do not decompose and take up landfill space.