13.5 Polymerisation of alkenes

• Addition polymerisation is the process of joining together many monomers to form a long chain of polymer molecules
• Addition polymerisation:

  • unsaturated alkene molecules undergo addition polymerisation to form long saturated polymer chain containing no double bonds
• monomer - a small molecule that combines with many other monomers to form a polymer
• repeat unit - the specific arrangement of atoms in the polymer molecule that repeats over and over again
• polymer - consists of many repeating units (monomers) joined together to make a long chain
• All addition polymers are chemically unreactive and not biodegradable
• Environmental concerns:

  • many alkene-based polymers are non-biodegradable due to their lack of reactivity

  Solutions:

  • recycling - conserves finite fossil fuels and decreases the amount of waste going to landfill. It is costly to sort by hand
  • feedstock recycling - reclaiming monomers from waste polymers which can be used as raw materials for the production of new polymers
• Biodegradable and photodegradable polymers:

  • Bioplastics are made from plant based materials so they are renewable and sustainable.
  • Biodegradable polymers are broken down by bacteria into water, carbon dioxide and biological compounds
  • Photodegradable polymers contain bonds which are weakened by absorbing light