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Learn0620Papers 2, 4 · ExtendedOrganic chemistryPolymers
Organic chemistry · Subtopic 5 of 5

Polymers

Polymers are very long molecules made by joining many small monomers. In addition polymerisation, alkene monomers open their C=C bonds and join, with no other product: ethene → poly(ethene). In condensation polymerisation, monomers with two functional groups join and a small molecule (usually water) is lost: dicarboxylic acids + diols → polyesters; + diamines → polyamides (nylon). Proteins are natural polyamides made from amino acids. Most plastics are non-biodegradable, causing litter, harm to wildlife and problems in landfill and incineration.

Cambridge 5070 Paper 1Cambridge 5070 Paper 2Cambridge 0620 Papers 2, 4Cambridge 0620 Papers 1, 3Edexcel 4CH1 Paper 1CEdexcel 4CH1 Paper 2C≈ 40 minRevision 1 · updated 2026-10-30
Section 1 of 14

Learning objectives

  • Describe addition polymerisation and draw repeat units.
  • Describe condensation polymerisation for polyesters and polyamides.
  • Identify proteins as natural polyamides.
  • Discuss the disposal of plastics.
Pause and think

A plastic bag and a polyester shirt are both polymers. Why does neither rot in a landfill?

Section 2 of 14

Core idea

Start hereChains of thousands

A single poly(ethene) molecule can contain over 100,000 carbon atoms. Joining small molecules into giant chains gives us plastics, fibres and, inside you, proteins.

The big idea

Addition polymers form when alkene monomers open their C=C bonds and link up. Condensation polymers form when two different monomers join and lose a small molecule such as water each time.

1. Addition polymers

Worked exampleFrom monomer to polymer

Tetrafluoroethene, CF2=CF2\mathrm{CF_2{=}CF_2}, polymerises.

Goal
Repeat unit and name.
Strategy
Open the C=C bond.
  1. −CF2−CF2−\mathrm{-CF_2-CF_2-}
    Double bond becomes single, with bonds to neighbours.
  2. −[CF2−CF2]n−\mathrm{-[CF_2-CF_2]_n-}
    Brackets and nn.
AnswerPoly(tetrafluoroethene), PTFE.
✓ CheckSame atoms as the monomer ✓.

2. Condensation polymers

Two types of condensation polymer

Water is lost at every link.

Exam tipTelling them apart One type of monomer with C=C and no by-product → addition. Two monomers with two functional groups each, and water lost → condensation.

3. Plastics and the environment

  • Landfill: non-biodegradable, persists for centuries.
  • Incineration: energy recovered but releases CO2\mathrm{CO_2} and toxic gases.
  • Litter: harms wildlife; microplastics.
  • Better: reduce, reuse, recycle; biodegradable polyesters.
Pause and think

Why can proteins in food be digested, but nylon can't?

Summary

  • Addition: alkene monomers.
  • Condensation: water lost.
  • Proteins are polyamides.
Key words
Monomer
Small molecule that joins to form a polymer.
Repeat unit
The section repeated along a polymer chain.
Biodegradable
Broken down by microorganisms.
HistoryAccidental polythene. Poly(ethene) was discovered by accident in 1933 at ICI when a high-pressure experiment leaked oxygen into ethene and left a white waxy solid.
Fun factTeflon in space. PTFE (Teflon) is so slippery and unreactive that it's used on non-stick pans, spacesuits and heart-valve implants.
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