polymers

• synthesis of polyesters

  • diol react with a dicarboxylic acid (or its derivatives such as acyl chlorides or acid anhydrides)
  • nucleophilic addition-elimination
  • condensation reactions make small molecules (like H2O, Cl2)
  • eg: terylene
• synthesis of polyamides

  • diamine react with a dicarboxylic acid (again can also react with acyl chlorides and acid anhydrides)
  • nucleophilic addition-elimination
  • condensation reaction with a small molecule by product
  • eg: kevlar and nylon
• synthesis of polypeptides

  • condensation reaction between amino acids
  • the amino acid contain an amine and a carboxylic acid group at either end, these two groups react and form an amide linkage
  • polypeptides then form proteins
• ways of disposing polymers

  1. incineration: buring to produce energy: reduces landfill space but makes toxic gases and greenhouse gases
  2. recycling: saves raw materials but must be seperated and organised (expensive)
  3. landfill: most common takes up space, very bad for polyalkenes as they biodegrade very slowly (polyesters and polyamides are more biodegradable). green house gases + water contamination
• biodegradability of polymers

  • polyalkenes have strong C-C and C-H bonds so biodegrade very slowly (are non-biodegradable)
  • polyesters and polyamides can be broken down by hydrolysis so are biodegradable. It has weak polar bonds in the polymer chain
  • acid hydrolysis (with H+) makes the original monomers
  • basic hydrolysis (with OH-) makes the salt of the dicarboxylic acid monomer
• kevlar


  (polyamide)

  • made from benzene-1,4-dicarboxylic acid and 1,4-diaminobenzime
  • used for bullet proof vests

  
• nylon 6,6


  (polyamide)

  • made from hexanedioic acid and 1,6-diaminohexane
  • used in ropes and fabric

  
• terylene


  (polyester)

  • made from benzene-1,4-dicarboxylic acid and ethane-1,2-diol
  • used in plastic bottles and clothes (PET)

  
• compare addition and condesation polymers IMF

  • ..

  
• adv of recycling polymers

  adv

  • cheaper than to make from scratch
  • less CO2 produced compared to incineration
  • preserves non renewable raw materials (crude oil)
  • reduces reliance on landfill
• dis of recycling polymers

  dis

  • plastics can be contaminated when recycled
  • difficult to remake original plastic
  • sorting and processing to be recycled is expensive
  • difficult to recycle due to variety of types of plastic