Chemistry • Year 12 • Module 7 • Lesson 22
Condensation Polymers: Polyesters & Polyamides
Secure the core vocabulary, the condensation mechanism, and the key monomers for PET and Nylon 6,6 before moving to application and analysis.
1. Label the condensation polymerisation diagram
The diagram below shows a single condensation step producing one ester linkage from a diol and a diacid. Write the missing labels into boxes A–H. Each label is drawn from the lesson’s Key Terms or from Cards 1–2. 8 marks
- A — type of functional group shown on left monomer fragment _______________________
- B — type of functional group shown on right monomer fragment _______________________
- C — name of the small molecule released _______________________
- D — name of the linkage formed (two-word answer) _______________________
- E — notation for the linkage (-___-) _______________________
- F — term for a monomer that has two reactive groups (one at each end) _______________________
- G — name of this type of polymerisation _______________________
- H — subscript letter on the square bracket denoting indefinite chain length _______________________
| Box | Your label |
|---|---|
| A | |
| B | |
| C | |
| D | |
| E | |
| F | |
| G | |
| H |
2. Term–definition match
The ten definitions below are shuffled. In the right-hand column write the matching term from this list: condensation polymerisation, polyester, polyamide, diol, dicarboxylic acid, ester linkage, amide linkage, degree of polymerisation, hydrolysis, bifunctional monomer. 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 2.1 | A compound carrying two hydroxyl groups (-OH), one at each end; one of the two monomers required to make a polyester. | |
| 2.2 | The -COO- group that links monomers in PET; formed when a hydroxyl group reacts with a carboxylic acid group. | |
| 2.3 | A condensation polymer formed by reaction between a diamine and a dicarboxylic acid, linked by -CO-NH- bonds; e.g. nylon-6,6. | |
| 2.4 | The reverse of condensation polymerisation; the addition of water across a linkage to regenerate the original monomers. | |
| 2.5 | The number of repeat units in a polymer chain; higher value generally means higher molar mass and higher melting point. | |
| 2.6 | A monomer that carries two reactive functional groups, one at each end, allowing chain growth from both ends. | |
| 2.7 | A condensation polymer formed by reaction between a diol and a dicarboxylic acid, linked by ester bonds; e.g. PET. | |
| 2.8 | A compound carrying two carboxylic acid groups (-COOH); reacts with a diol (for polyester) or diamine (for polyamide). | |
| 2.9 | The -CO-NH- group linking monomers in nylon; also called a peptide bond in proteins; formed when an amine reacts with a carboxylic acid. | |
| 2.10 | Polymerisation in which monomers react with each other with the loss of a small molecule (usually water or HCl) at each bond formed; monomers must be bifunctional. |
3. True or false — with correction
For each statement, circle T or F. If the statement is false, write the corrected version on the line below. 8 marks (1 for T/F, 1 for the correction where needed)
3.1 In addition polymerisation, every atom of the monomer ends up in the polymer chain with no by-product. T / F
3.2 PET is made from two monomers: ethylene glycol (HOCH₂CH₂OH) and hexanedioic acid. T / F
3.3 Nylon 6,6 contains two amide linkages per repeat unit. T / F
3.4 Condensation polymers can be hydrolysed because their ester or amide bonds can be cleaved by water; addition polymers cannot because their C-C bonds do not react with water. T / F
4. Function recall
Answer each in 1–2 sentences using precise terms from the lesson. 10 marks (2 each)
4.1 What is the role of bifunctionality in condensation polymerisation? Why does each monomer need two reactive groups?
4.2 What functional groups react to form an ester linkage, and what small molecule is released?
4.3 What functional groups react to form an amide linkage, and what small molecule is released?
4.4 Name both monomers of Nylon 6,6, including their functional groups, and explain what “6,6” refers to.
4.5 Why do PET drink bottles (recycling code 1) present a smaller long-term environmental persistence problem than polyethylene (recycling code 4), at a chemical level?
5. Build a concept map
Draw labelled arrows between the six terms below to show how they connect. Each arrow must carry a linking phrase (e.g. “forms when”, “releases”, “is hydrolysed by”). Aim for at least 6 labelled arrows. 6 marks
Supplied terms: condensation polymerisation · bifunctional monomer · ester / amide linkage · water (H₂O) · hydrolysis · polymer chain.
6. Fill the blank — cloze passage
Complete the passage by writing the correct term from the word bank into each blank. Each term is used once only. 8 marks
Word bank: water • amide • ester • bifunctional • condensation • hydrolysed • terephthalic acid • hexane-1,6-diamine
In _________________ polymerisation, each monomer must be _________________ — it must carry two reactive groups, one at each end of the molecule. When the two monomers react, a _________________ linkage (-COO-) or an _________________ linkage (-CO-NH-) forms between them, and a molecule of _________________ is released as a by-product. The polyester PET is made from ethylene glycol and _________________, while the polyamide Nylon 6,6 is made from _________________ and hexanedioic acid. Because the linkages in condensation polymers contain a susceptible C-O or C-N bond, these polymers can be _________________ by acid, base, or enzymes — the reverse of their formation reaction.
Q1 — Labelled diagram
A: hydroxyl group (-OH). B: carboxylic acid group (-COOH). C: water (H₂O). D: ester linkage. E: -COO- (or -C(=O)-O-). F: bifunctional monomer. G: condensation polymerisation. H: n.
Q2 — Term–definition matches
2.1 diol • 2.2 ester linkage • 2.3 polyamide • 2.4 hydrolysis • 2.5 degree of polymerisation • 2.6 bifunctional monomer • 2.7 polyester • 2.8 dicarboxylic acid • 2.9 amide linkage • 2.10 condensation polymerisation.
Q3 — True / false with correction
3.1 True.
3.2 False. Correction: PET is made from ethylene glycol and terephthalic acid (benzene-1,4-dicarboxylic acid, HOOC-C&sub6;H&sub4;-COOH), not hexanedioic acid. Hexanedioic acid is used for Nylon 6,6.
3.3 True. Each repeat unit [-NH-(CH₂)&sub6;-NH-CO-(CH₂)&sub4;-CO-]n has an amide linkage at each end of the diacid component — two amide bonds per repeat unit.
3.4 True.
Q4.1 — Bifunctionality
Bifunctionality is required so that the chain can grow from both ends of each monomer simultaneously. If a monomer had only one reactive group, it could bond to another monomer only once and the chain would terminate at that point. Two reactive groups (one at each end) means each monomer can bond to a different partner at each end, allowing the chain to extend indefinitely in both directions.
Q4.2 — Ester linkage formation
A hydroxyl group (-OH, from the diol) reacts with a carboxylic acid group (-COOH, from the diacid). The H from the hydroxyl and the OH from the carboxylic acid combine and leave as water (H₂O). The oxygen from the diol -OH bonds to the carbonyl carbon, forming the ester linkage -COO-.
Q4.3 — Amide linkage formation
An amine group (-NH₂, from the diamine) reacts with a carboxylic acid group (-COOH, from the diacid). The H from the amine and the OH from the carboxylic acid leave as water (H₂O). The nitrogen bonds to the carbonyl carbon, forming the amide linkage -CO-NH-.
Q4.4 — Nylon 6,6 monomers and naming
Monomer 1: hexane-1,6-diamine (H₂N-(CH₂)&sub6;-NH₂) — 6-carbon chain with an -NH₂ group at each end. Monomer 2: hexanedioic acid (HOOC-(CH₂)&sub4;-COOH) — 6-carbon chain (including the two carbonyl carbons) with -COOH at each end. “6,6” refers to the 6 carbons in the diamine monomer and the 6 carbons in the diacid monomer.
Q4.5 — PET vs polyethylene environmental persistence
PET contains ester linkages (-COO-) which can be slowly hydrolysed by water under acidic or alkaline conditions, or cleaved by esterase / PETase enzymes. A degradation pathway therefore exists, even if it is slow at ambient conditions. Polyethylene has only C-C and C-H bonds; no ester or amide group is present for water or enzymes to attack. Polyethylene can only fragment through UV photodegradation into microplastics — no chemical breakdown. Hence PET bottles have a slightly lower inherent persistence than polyethylene bottles at the chemical-linkage level.
Q5 — Sample concept map
A correct map should include arrows such as:
- condensation polymerisation — requires → bifunctional monomer
- condensation polymerisation — produces → polymer chain
- condensation polymerisation — releases → water (H₂O)
- bifunctional monomer — forms → ester / amide linkage
- ester / amide linkage — is broken by → hydrolysis
- hydrolysis — uses → water (H₂O)
- polymer chain — contains repeating → ester / amide linkage
Award full marks for at least 6 correctly labelled arrows with causally accurate direction.
Q6 — Cloze answers (in order)
condensation • bifunctional • ester • amide • water • terephthalic acid • hexane-1,6-diamine • hydrolysed.