Biodegradable polyesters
2 marks · HardDescribe how the biodegradable polyester polylactic acid (PLA) can be made from its monomer, lactic acid. In your answer, state the name of both the process and the type of chemical reaction involved.
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Also accept: Through condensation polymerisation, lactic acid monomers react by removing water to form ester linkages, creating PLA.; PLA is formed by condensation polymerisation of lactic acid, where each reaction releases one molecule of water and forms an ester bond.
Common mistakes: Stating addition polymerisation instead of condensation.; Omitting mention of water being removed.
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Marking points
M1 · 1 mark · Correctly identifies the process as condensation polymerisation and describes that lactic acid monomers react together.
A1 · 1 mark · Explains that the reaction involves the removal of water to form ester linkages (or equivalent description of forming an ester bond).
Worked solution
Polylactic acid (PLA) is made by condensation polymerisation of lactic acid monomers.
During this reaction, each time two lactic acid molecules react, a molecule of water is released, and an ester linkage forms between them.