A pharmaceutical company uses condensation polymerisation to produce polyamide fibres for use in surgical sutures (stitches that dissolve inside the body). Explain why polyamides are classed as condensation polymers and describe the structural requirements of the monomers needed to form them.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Polyamides are a group of condensation polymers. Unlike addition polymers, they are formed when monomers containing two functional groups react together, releasing small molecules in the process. Surgical sutures made from polyamides are designed to break down naturally inside the body over time.
Model answer (5 marks)
Polyamides are condensation polymers because the polymerisation reaction joins monomers together while eliminating a small molecule.
1. During the reaction a water molecule is released.
2. Each monomer must be bifunctional – it contains two reactive groups.
3. One end of the monomer (or one end of two different monomers) carries an –NH₂ (amine) group.
4. The other end carries a –COOH (carboxylic acid) group.
5. The amine reacts with the carboxyl group to give an amide linkage, forming the polymer chain.
These structural requirements ensure that the monomers can link in a step‑wise fashion, producing the polyamide fibre used for dissolving sutures.
1. During the reaction a water molecule is released.
2. Each monomer must be bifunctional – it contains two reactive groups.
3. One end of the monomer (or one end of two different monomers) carries an –NH₂ (amine) group.
4. The other end carries a –COOH (carboxylic acid) group.
5. The amine reacts with the carboxyl group to give an amide linkage, forming the polymer chain.
These structural requirements ensure that the monomers can link in a step‑wise fashion, producing the polyamide fibre used for dissolving sutures.
Examiner tips
- Use the word ‘condensation’ and mention water as the by‑product; this shows you know the definition. Show the two functional groups and explain that they must be on the same monomer (bifunctional) or on two different monomers. Mention the amide bond as the link formed. Keep the answer concise – 5 points can be covered in 5 short sentences.
Common mistakes
- Forgetting to state that water is the small molecule released. Saying the monomers are ‘monofunctional’ or omitting the requirement for both –NH₂ and –COOH. Using vague terms like ‘reactive groups’ without naming the amine and carboxyl groups.
Mark scheme (5 marks)
- Condensation polymerisation involves monomers joining together and losing/releasing small molecules
- Water is named as the small molecule released
- Each monomer must contain two functional groups (bifunctional monomers)
- One type of monomer (or both ends of the same monomer) contains an amine/–NH₂ group that reacts with the other functional group
- The other functional group is a carboxylic acid/–COOH group, which reacts with the amine group to form the amide bond/link
Key terms in this question
condensation polymerisation · monomer · polyamide
Related
- All OCR A-Level Chemistry B: Salters (H433) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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