Polymers and Chemistry in Everyday Life
This domain pairs polymer classification and named industrial polymers with the pharmacology vocabulary of everyday chemicals.
Polymer classes
- addition polymers form by chain growth: polyethene, PVC, polystyrene, teflon
- condensation polymers form by step growth with loss of a small molecule: Nylon-6,6, PET, Bakelite
- homopolymer versus copolymer; elastomers versus fibres versus thermosetting plastics
- free-radical polymerisation: initiation, propagation, termination (benzoyl peroxide initiator)
- Ziegler–Natta catalysts give stereoregular polymers; Buna-S and Buna-N are copolymers
Natural and special polymers
- natural rubber is cis-polyisoprene; vulcanisation with sulphur creates cross-links and raises strength
- starch, cellulose, proteins and nucleic acids are biopolymers
- biodegradable polymers include PHBV and Nylon-2-nylon-6
Everyday chemistry
- analgesics: aspirin, paracetamol; antibiotics: penicillin, chloramphenicol; antiseptics: dettol, bithional
- artificial sweeteners: saccharin, aspartame, sucralose
- soaps are sodium salts of fatty acids and precipitate scum in hard water; synthetic detergents avoid this
Worked example
Nylon-6,6 is made from adipic acid (hexanedioic acid) and hexamethylenediamine. Each acid end condenses with an amine end, releasing water and forming an amide linkage, so the polymer is a polyamide with six carbons in each repeat unit. Because it is a condensation polymer, the reaction needs controlled heating and gives off water - unlike the addition polymerisation of ethene.
Traps that cost marks
- Classifying Bakelite or PET as addition polymers.
- Confusing the role of aspirin (analgesic) with that of penicillin (antibiotic).
- Forgetting that natural rubber is the cis isomer and that vulcanisation introduces sulphur cross-links.