C29 polymerisation

• condensation polymers form when a water molecule or a hydrogen chloride molecule is removed from the species in the reaction
• there are three main types of condensation polymer: polyamide, polyester, polypeptide
• polyesters are formed from a reaction between a dicarboxylic acid and a diol
• when a polyester is formed, a water molecule is removed which leaves an ester linkage
• an ester linkage is -COO-
• a common polyester is terylene (PET), made from benzene-1,4-dicarboxylic acid and ethane-1,2-diol, it is used for fabrics and bottles
• polyamides are formed from a reaction between a dicarboxylic acid and a diamine
• when a polyamide is formed, a water molecule is removed which leaves an amide linkage
• an amide linkage is -CONH-
• common polyamides are:

  • nylon-6,6 made from 1,6-diaminohexane and hexane-1,6-dicarboxylic acid, used for fabrics
  • kevlar, made from 1,4-benzenedicarboxylic acid and 1,4-benzenediamine, used for bullet-proof vests and stab-proof clothing
• polyamides are strong because they are typically made from long chain molecules
• polypeptides are formed from a reaction between an amino acid and another amino acid
• when a polypeptide is formed, a water molecule is removed which leaves a peptide bond
• a peptide bond is -CONH-
• condensation polymers can be broken back down into their constituent molecules by the addition of water, because water is attracted to the polar regions of the polymer so the links can be broken down, so they are susceptible to hydrolysis and nucleophilic attack
• condensation polymers contain polar bonds, they can also have hydrogen bonds and dipole-dipole forces between separate polymer chains, holding them together in a strong structure
• all polymers are useful but can be hard to get rid of as waste products
• polyalkenes are very inert with non-polar bonds so are non-biodegradable
• polyalkenes have to be broken down by burning which produces pollutants such as SO2 and CO2
• polyesters, polyamides and polypeptides have polar bonds so are biodegradable by water or moisture, so they can be put in landfill and will gradually break down
• some plastics can be recycled, this saves natural resources and reduces the amount of waste in landfill, but it is difficult and time-consuming as everything needs to be washed and sorted before it can be recycled
• kevlar has hydrogen bonding between its chains