Polymers

• One of the most important that chemicals from crude oil are used is to make polymers.
• monomer


  a small molecule that can join together to form a polymer

  (mono = one)
• polymer


  large molecules formed when lots of smaller monomer molecules join together
• By using different monomers, you can make various types of polymers that have very different properties
• Monomers come from cracking crude oil, alkenes
• when we say a monomer we don't mean one of them, we mean 1000's of them only not joined together.
• monomer:

  ethene

  --->

  polymer:

  poly(ethene)
• ethene is the smallest unsaturated hydrocarbon molecule. It can be made to use polythene/poly(ethene)
• poly(ethene) is strong and easy to shape and is clear unless colouring is added. Examples of uses:

  • 'plastic' carrier bags
  • drinks bottles
  • dustbins
  • washing-up bowls
  • cling film
• poly(propene) is a very strong, tough plastic. Examples of uses:

  • carpets
  • milk crates
  • ropes
• addition polymerisation


  when many monomers join together to form a large molecule
• • When alkene molecules join together, the double covalent bond between two carbon atoms 'opens up'.
  • It is replaced by a single carbon-carbon covalent bond between the two carbon atoms.
  • Thousands of molecules join together end to end.
  • The polymer chains they form are made up of a 'backbone' of carbon atoms.
  • This type of reaction is called an addition polymerisation and forms addition polymers.
• In addition polymerisation reactions only one product is formed.
• In addition polymerisation reaction:

  • the repeating unit and the monomer units contain the same atoms
  • the percentage atom economy is 100%
• In condensation polymerisation, you can have two different reactants and you form two products, the polymer and another smaller molecule (commonly water)
• The two different functional groups of the reacting monomers need to react together. This is how the long polymer chains are formed.
• To make a polyester we want to join many esters in a long chain, for this they need a functional group at both ends - a diol if it's an alcohol as the monomer and a dicarboxylic acid when the monomer is a carboxylic acid.
• Important factor in condensation polymerisation:

  • each of the monomers has to have at least 2 functional groups
  • there has to be 2 different functional groups overall.
• polyesters are generally biodegradable since bacteria and other microorganisms can break down the esters inside.
• In condensation polymerisation, monomers link together as they polymerise by 'ester links', and a water molecule is given off as each link is made in the reaction.
• Making nylon

  1. Put a thin layer of monomer A into the bottom of a very small beaker.
  2. Carefully pour a layer of monomer B on top of this.
  3. Gently draw a thread out of the beaker using a pair of tweezers
  4. Wind it around a test tube.

  Safety:

  Wear gloves and eye protection. do not touch the nylon formed. Carry out in a fume cupboard or a well-ventilated lab.
• The fumes given off as the two monomers react to form nylon is hydrogen chloride gas which is toxic. This is an example of a small molecule given off in a condensation reaction.
• When drawing addition polymers, draw the bonds of the monomer up and down rather than at angles.
• Natural polymers

  • cellulose
  • starch
  • proteins
  • DNA
  • amino acids
• polypeptides -> amino acids

  DNA -> nucleotides

  carbohydrates -> sugars
• Polypeptides fold up to form a protein made up of lots of different animo acids. It will then combine with many other polypeptides in many different combinations. This can do a range of things:

  • catalysing chemical reactions as enzymes
  • providing structure and strength to tissues
• Adjacent amino acids can join together to through condensation reactions.

  The bond produced can be called an 'amide bond', 'amide link' or a 'peptide bond'
• DNA is made up of monomer called nucleotides (4 different types)

  T, A, G, C

  These form in different orders to form different codes (genes)
• To prevent them getting damaged, two polymer chains link together.

  This double strand naturally coils to form a double helix.
• Carbohydrate is a general term that refers to ' a number of different polymers and monomers that we derive energy from'
• Carbohydrates are all made up of:

  • carbon
  • oxygen
  • hydrogen
• What makes up carbohydrates

  Polymers: 'polysaccharides'

  • starch
  • cellulose
  • glycogen

  Monomers: 'monosaccharides' (sugars)

  • glucose
  • fructose