Used in: clothing, ropes, parachutes, gear wheels.
SILK and WOOL:
Natural polyamides — proteins made from amino acid monomers joined by peptide bonds (amide links).
The same chemistry as nylon but with different monomers.
PROPERTIES OF CONDENSATION POLYMERS:
Can be broken down (hydrolysed) by water under the right conditions — more biodegradable than addition polymers in some cases.
Strong intermolecular forces (H-bonding in polyamides) → high melting points, strong fibres.
Comparing Addition and Condensation Polymerisation
PROPERTY | ADDITION | CONDENSATION
Monomer requirement | C=C double bond | Two functional groups
By-products | None | Water (or HCl)
Atom economy | 100% | < 100%
Linkage type | C–C backbone | Ester (–COO–) or amide (–CONH–)
Examples | Poly(ethene), PVC, nylon | PET, nylon-6,6, proteins, DNA
Biodegradability | Generally non-biodegradable | Some can be hydrolysed
Note: Nylon is made by condensation polymerisation (amide links) — NOT addition polymerisation.
INDUSTRIAL IMPORTANCE:
PET recycling: PET bottles can be depolymerised (broken down) by hydrolysis → monomers recovered → repolymerised.
This makes condensation polymers potentially more recyclable than addition polymers.
DRAWING CONDENSATION POLYMER REPEAT UNITS:
Identify the two monomers → show them joining → remove water → draw the repeat unit in brackets with n.
⚠️ Common Mistake
Condensation polymerisation ALWAYS produces a small molecule (usually water) as a by-product — it is NOT 100% atom economy unlike addition polymerisation. The ester link in polyesters is –COO–; the amide link in polyamides is –CONH–. Don't confuse the two.
📐 Key Equations
Diol + Diacid → Polyester + water
Diamine + Diacid → Polyamide + water
📌 Key Note
Condensation: two functional groups per monomer + small molecule (H₂O) lost at each junction. Polyester: diol + diacid, ester links. Polyamide: diamine + diacid, amide links (e.g. nylon). Atom economy < 100%. Contrast with addition: C=C monomers, 100% atom economy. Natural proteins and DNA are condensation polymers.
🎯 Matching Activity — Addition vs Condensation Polymerisation
Match each property to addition polymerisation, condensation polymerisation, or both. — drag the symbols on the right to match the component names on the left.
Addition only
Drop here
Condensation only
Drop here
Addition only
Drop here
Condensation only
Drop here
Both
Drop here
Ester or amide links form between monomers
100% atom economy — all atoms end up in the polymer
Many monomers join to form a very large polymer molecule
Monomers must contain a C=C double bond
A small molecule (usually water) is released at each monomer junction
⭐ Higher Tier Only
HT only — write balanced equations for specific condensation polymerisations. Draw repeat units of polyesters and polyamides. Explain why condensation polymers can potentially be hydrolysed/recycled. Evaluate the environmental advantages of condensation polymers compared to non-biodegradable addition polymers.
🔬 Triple Science Only
Condensation polymerisation (4.7.3.2) is chemistry-only AND HT only — not in Combined Science at any tier.
🎯 Test Yourself
Question 1 of 2
1. What type of link forms in a polyester and what are the two monomers needed?
2. Why does condensation polymerisation have a lower atom economy than addition polymerisation?
⭐ How Well Do You Understand This Topic?
Be honest with yourself — this helps you know what to revise!
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