Polymers
Polymers
- A polymer is a very large molecule built from many small monomers.
- Addition polymerisation: many unsaturated monomers join with no other product (e.g. ethene → poly(ethene)). The repeating part is the repeat unit.
Practice
A polymer is made from many small molecules called:
Monomers join together to build a polymer; the repeating part is the repeat unit.
Practice
In addition polymerisation, the monomers:
Addition polymerisation joins unsaturated monomers (C=C opens up) with no by-product.
Condensation polymerisation
- Monomers join and a small molecule (usually water) is lost each time.
- Polyamides (e.g. nylon) — from a dicarboxylic acid + a diamine.
- Polyesters (e.g. PET) — from a dicarboxylic acid + a diol; can be broken back to monomers.
- Proteins are natural polyamides (from amino acid monomers).
Practice
In condensation polymerisation, a small molecule is lost — usually:
Condensation polymers (polyamides, polyesters) form by losing a small molecule, usually water.
Plastics and the environment
- Many plastics don't break down: they fill landfill, harm sea life, and burning them can make toxic gases.
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Key idea
- a polymer is built from many monomers; addition = unsaturated monomers join, no other product
- condensation loses a small molecule (water): polyamides (nylon), polyesters (PET); proteins are natural polyamides
- many plastics don't break down → an environmental problem