Polymers
Polymers
This domain tests classification, monomers, polymerisation type and the properties of commercially important polymers.
Core rules
- Addition polymers form without loss of any small molecule; the empirical formula equals that of the monomer.
- Condensation polymers form with loss of water or another small molecule and are often copolymers.
- Nylon-6,6: adipic acid + hexamethylenediamine, with amide linkages.
- Terylene (PET): terephthalic acid + ethylene glycol, with ester linkages.
- Bakelite: phenol + formaldehyde, thermosetting.
- Buna-S: butadiene + styrene; neoprene: chloroprene; natural rubber: isoprene.
- Vulcanisation uses sulphur to form cross-links, increasing strength and elasticity.
Worked example Identify the polymer and its monomers: a polymer with repeating units containing –CO–NH– and made from a six-carbon diacid and a six-carbon diamine. The amide link identifies a polyamide; the six-carbon diacid is adipic acid, HOOC(CH₂)₄COOH, and the diamine is hexamethylenediamine, H₂N(CH₂)₆NH₂. The polymer is nylon-6,6, formed by condensation with loss of water.
Traps
- Calling bakelite thermoplastic.
- Confusing addition and condensation polymerisation.
- Forgetting that natural rubber is cis-1,4-polyisoprene.