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Properties of Polymers

Chemistry: AQA A Level, topic 5.4.4

Names and Properties of Polymers

Addition polymers have specific properties. We can control these properties to create useful materials. They also have a simple naming system.

Naming

Naming

  • Just as poly(ethene) is made from ethene, other polymers like poly(phenylethene) are made from phenylethene.
  • This is a general pattern. If you polymerise a molecule, its polymer is just poly(name of molecule).
Intermolecular forces

Intermolecular forces

  • Polymers are bound by van der Waals forces.
  • The intermolecular forces are strong as the molecules are huge so there are lots of van der Waals forces between them!
Types of addition polymers

Types of addition polymers

  • There are two broad classes of addition polymers:
  • Straight-chain polymers (e.g. poly(ethene)).
    • Straight-chain polymers pack closely together and are strong and rigid.
  • Branched-chain polymers.
    • Branched-chain polymers pack less densely and are more flexible.
Reactivity of addition polymers

Reactivity of addition polymers

  • Addition polymers are often unreactive.
  • This is because if the monomers were reactive, we'd get lots of side reactions during polymerisation.
  • Addition polymers are NOT very reactive because the carbon chain is saturated and the side chains are usually non-polar.

Modifying Polymer Properties

The properties of polymers can be modified using plasticisers.

Plasticisers

Plasticisers

  • We can make straight-chain polymers more flexible using plasticisers.
  • Plasticisers are molecules that stick between the chains and keep the polymers further apart from each other.
  • This weakens the van der Waals forces and lets the chains slide more easily. This means that the polymers are more flexible.
Poly(chloroethene)

Poly(chloroethene)

  • Poly(chloroethene) is also called PVC because this polymer used to be called poly(vinylchloride).
  • PVC is used for rigid plastics like drainpipes. This is because it has strong dipole-dipole forces due to the presence of the chlorine atom.
  • If you add a plasticiser, you can make more flexible PVC materials, which can be used in flooring tiles.

Test yourself on Properties of Polymers

  • Which of the following is present between polymers?

  • Which of the following is true of polymers?

  • What do plasticisers improve in the polymers?

  • What effects do plasticisers have on polymers?

  • Why is PVC so rigid?

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