Polymers

9.17C Recall that…
  • A polymer is a substance of high average relative molecular mass made up of small repeating units
9.18C Describe: how ethene molecules can combine together in a polymerisation reaction and that the addition polymer formed is called poly(ethene) (conditions and mechanisms not required)
  • Alkenes can be used to make polymers such as poly(ethane) and poly(propene) by addition polymerisation. In this reaction, many small molecules (monomers) join together to create very large molecules (polymers). For example:

  • The repeat unit has the same atoms as the monomer because no other molecule is formed in the reaction
9.19C Describe how other addition polymers can be made by combining together other monomer molecules containing C=C, to include poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE) (conditions and mechanisms not required)

9.20C Deduce the structure of a monomer from the structure of an addition polymer and vice versa
  • Monomer is just repeat unit, replacing C-C with C=C and removing brackets and “n”
9.21C Explain how the uses of polymers are related to their properties and vice versa: including poly(ethene), poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE)
  • Poly(ethene)
    • Properties: flexible, cheap, electrical insulator
    • Uses: plastic bags and bottles, coating on electrical wires
  • Poly(propene)
    • Properties: flexible & strong
    • Uses: buckets and crates
  • Poly(chloroethene) or PVC
    • Properties: tough, cheap and long lasting
    • Uses: window frames
  • PTFE
    • Properties: tough & non-stick
    • Uses: non-stick coating on pans
9.22C (HT only) Explain:
  • Why polyesters are condensation polymers
    • Alcohol and carboxylic acid functional groups react, losing a small molecule – water
    • This is an ester – therefore a polyester is a lot of these monomers (esters), which is thus a condensation polymer
  • How a polyester is formed when a monomer molecule containing two carboxylic acid groups is reacted with a monomer molecule containing two alcohol groups
    • -OH + -COOH -> -COO- (+H2O removed)
  • How a molecule of water is formed each time an ester link is formed

See example below:

9.23C Evaluate the advantages and disadvantages of recycling polymers, including economic implications, availability of starting materials and environmental impact
  • Advantages
    • Reuse waste materials – better for environment than burning them or putting them in landfills
    • Saves crude oil (a finite resource)
    • More economically viable instead of making more polymers
  • Disadvantages
    • Difficult and expensive to first separate the different polymers
9.25C Recall that:
  • DNA is a polymer made from 4 different monomers called nucleotides (names of nucleotides not required)
  • Starch is a polymer based on sugars
  • Proteins are polymers based on amino acids