Polymers — Addition and Condensation

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CognitoAddition and condensation polymers

Key facts & methods

Addition polymers (recap)

Made from alkene monomers — the C=C double bond opens and monomers join.
n(CH2=CH2) → -(CH2-CH2)n- (poly(ethene))
Only one type of monomer needed. No other products (100% atom economy).
Examples: poly(ethene), poly(propene), poly(chloroethene/PVC), poly(tetrafluoroethene/PTFE).
Most are non-biodegradable — major environmental problem.

Condensation polymers

Two different monomers react together. A small molecule (water or HCl) is released each time two monomers join.
Polyesters: dicarboxylic acid + diol → polyester + water. E.g. PET (polyethylene terephthalate).
Polyamides: dicarboxylic acid + diamine → polyamide + water. E.g. Nylon, Kevlar.
The link between monomers: ester link (-COO-) in polyesters; peptide/amide link (-CONH-) in polyamides.

Natural polymers

DNA: condensation polymer of nucleotides. Stores genetic information.
Proteins: condensation polymer of amino acids. Joined by peptide bonds.
Starch and cellulose: condensation polymers of glucose. Starch = storage; cellulose = structural.
Biodegradable polymers: some condensation polymers can be broken down by microorganisms.
Thermoplastics: can be remoulded on heating. Thermosetting: permanently set structure.

Exam questions — 4 questions · 10 marks · AQA 8462 style

1 markCondensation vs additionAQA 8462

What is produced in addition to the polymer chain during condensation polymerisation?

A Nothing — all atoms go into the polymer

B A small molecule such as water

C An alkene monomer

D Carbon dioxide

3 marksIdentify polymer typeAQA 8462

A polymer is formed from two monomers: a dicarboxylic acid and a diol. (a) What type of polymerisation is this? (b) What small molecule is eliminated? (c) What type of bond links the monomers? (3 marks)

+30 XP

1 markEnvironmental issueAQA 8462

Why are most addition polymers an environmental problem?

A They are too expensive to produce

B They are non-biodegradable — they persist in the environment for hundreds of years

C They react dangerously with water

D They are toxic to humans

4 marksCompare two polymer typesAQA 8462

Compare addition polymerisation and condensation polymerisation in terms of: (a) type of monomer, (b) whether any by-product is formed, (c) an example of each. (3 marks)

Hint: Three parallel comparisons. Be specific: name types of monomer, state whether by-product exists, give a named example of each.

+40 XP

Polymers — Addition and Condensation

Addition polymers (recap)

Condensation polymers

Natural polymers

Module complete! 🎉