Chapter 21 - Polymers

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Addition Polymerisation

^ When multiple alkenes break their double bonds and join to create one long hydrocarbon.

  • The chain can vary in length as more and more double bonds break. A formula is used to show how big the molecule is without having to draw it out fully. 

The formula for poly(ethene) is 

The formula for poly(propene) is

The formula for poly(chloroethene) is 

Uses for these molecules:

  • Poly(ethene) - Plastic bags and bottles.
  • Poly(propene) - Ropes and crates (stronger than poly(ethene)).
  • Poly(chloroethene) - Drainpipes, windows, floor coverings and clothing.

Working out the monomer of a polymer:

  • Separate off two carbons and what they are bonded with above and below them. Then add the double bond back in to create an alkene.
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Condensation Polymerisation

In condensation polymerisation, there are two different monomers that join rather than just one. Each time a pair join together a small molecule [made from a combination of atoms off the end of each monomer] is lost.

Making Nylon:

  • The first monomer is from the dicarboxylic acid group (meaning it has two -COOH molecules is it [one at each end]). This is HOOCCH2CH2CH2CH2COOH.
  • The second is a diamine called 1,6-diaminohexane. The amino group is -NH2.                               It looks like this:  H2NCH2CH2CH2CH2CH2CH2NH
  • When they join, a water molecule is lost.
  • When drawn out, the joining of these two monomers looks like this:
  • .
  • .
  • .
  • .
  • However it can be drawn as a block diagram (representing the CH2 parts as a box) so that it is simpler to understand.
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