# A food packaging company is developing a new biodegradable material to replace single-use plastics. They decide to use condensation polymerisation to produce a polyester from two different monomers: a diol and a dicarboxylic acid. Explain how the structure of these monomers allows condensation polymerisation to occur, and describe the key features of the polyester polymer that is formed.

> OCR A-Level Chemistry B: Salters (H433) — 6.2 Nitrogen compounds, polymers and synthesis · Explain · 5 marks

> Condensation polymerisation is used to make polyesters from monomers containing two functional groups. A small molecule is lost each time two monomers join together.

## Mark scheme (5 marks)

1. Each monomer must have two functional groups (one at each end of the molecule)
2. The two different functional groups (–OH and –COOH) react together to form a bond between monomers
3. A small molecule (water) is lost / eliminated each time two monomers join
4. Because each monomer has two functional groups, the chain can extend in both directions to form a long-chain polymer
5. The resulting polyester contains an ester linkage / –COO– repeating unit in its backbone

## Key terms

- [condensation polymerisation](https://www.gradenine.co.uk/glossary/condensation-polymerisation)
- [monomer](https://www.gradenine.co.uk/glossary/monomer)
- [polyester](https://www.gradenine.co.uk/glossary/polyester)

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-food-packaging-company-is-developing-687e89a7) · Published by Druglandscape Ltd.