Condensation Polymers

• condensation polymers are made up of lots of individual monomers. with polyesters its common to use two different monomers.

  
• In order for dicarboxylic acid and diol to combine, dicarboxylic acid has to give up its OH group and diol has to give up its H from its OH group. When these 3 atoms combine they form a water molecule. This leaves the carbon from the dicarboxylic acid to bond directly with the oxygen from the diol. This is the bond that we call the ester link.

  
• To show the 2 different monomers bonded as a repeating unit and not as a dimer ( 2 monomers combined ), we need to remove the O and OH from the end and replace them with empty bonds. This will form another water molecule. To finish add large brackets to show the repeating unit. For example:

  
• In summary a condensation polymer is formed by a dicarboxylic acid monomer and diol monomer. When it is formed it will have 2 water molecules.

  
• To show how many we have we can use an n in front of the dicarboxylic acid and an n in front of the diol. Also an n behind the condensation polymer, and a 2n in front of the water. The n can be exchanged for a numerical value.

  
• We call them condensation polymers because they form water molecules
• In order for molecules to combine in condensation polymers there are a few important things:

  • Each of the monomers has to have at least two functional groups
  • There needs to be at least two different functional groups overall
  • A small molecule is given off during the process
  • Below is a real example:

  
• Condensation polymers are generally biodegradable because bacteria and microorganisms can break down the ester links. BUT addition polymers like plastics are not biodegradable.
• Condensation polymers can be made by joining together dicarboxylic acid monomers and diol monomers. These monomers are joined together by ester links.
• What can a box in the structure of a molecule be?

  The rest of the molecule in simplified form

  the

  
• diol monomer

  
• dicarboxylic acid monomer

  
• A dimer is two monomers combined
• When is a polymer referred to as a 'condensation' polymer?

  When water is a produced as a by-product of the reaction
• To make a polyester condensation polymerisation, the monomers need to have enough carboxylic acid and alcohol functional groups to form a long continuous chain. This means that each monomer needs to have at least two functional groups.

  
• Drawing of a condensation polymer