Making a polyester
2 marks · HardDescribe the main structural features that all polyesters have in common. Suggest why these features are important for the properties and uses of polyesters.
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All polyesters have a long-chain backbone with many ester links (–COO–) between repeating units. These strong covalent bonds along the polymer chain give polyesters durability and make them useful for fabrics and containers.
Also accept: Many ester groups joining repeating units in a long chain; the strong bonds give useful properties; Repeating units joined by ester bonds; this gives them strength and flexibility
Common mistakes: Mentioning carbon–carbon double bonds instead of ester links; Not relating structure to properties
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Marking points
B1 · 1 mark · Mentions long chains with repeating units connected by ester (–COO–) groups
B2 · 1 mark · Links presence of ester bonds/structure to useful properties such as strength/durability/flexibility
Worked solution
All polyesters consist of long chains made up of smaller units joined by ester links (–COO– bonds).
These ester links give the polymer its strength and durability, making polyesters suitable for a range of uses like fabrics and bottles.