Polymers and Chemistry in Everyday Life
Domain 14: Polymers and Chemistry in Everyday Life
This domain tests polymer classification, important commercial polymers, and the chemistry of drugs, antibiotics, antiseptics, soaps, and detergents.
Core rules
- Addition polymers form without loss of small molecules: polythene from ethene, PVC from vinyl chloride, polystyrene from styrene. Condensation polymers lose water or another small molecule: nylon-6,6 from adipic acid and hexamethylenediamine; terylene from ethylene glycol and terephthalic acid.
- Homopolymer has one monomer; copolymer has two or more. Buna-S and Buna-N are copolymers. Vulcanisation cross-links rubber with sulfur.
- Thermoplastics soften on heating; thermosetting polymers such as Bakelite and melamine are cross-linked and do not.
- Biodegradable polymers include PHBV and polylactic acid; they reduce persistence in the environment.
- Drugs: analgesics relieve pain, antibiotics treat bacterial infections, antiseptics kill or inhibit microbes on living tissue, disinfectants act on non-living surfaces. Soaps are salts of fatty acids; detergents are synthetic surfactants and can be biodegradable or non-biodegradable.
Worked example
Nylon-6,6 is a condensation polymer. Adipic acid (HOOC–(CH2)4–COOH) and hexamethylenediamine (H2N–(CH2)6–NH2) react repeatedly to form amide linkages, releasing H2O. The 6,6 refers to six carbons in each monomer, not six repeating units. Because the polymer has amide bonds, it is a polyamide.
Traps
- Calling nylon an addition polymer.
- Confusing monomer with repeating unit.
- Thinking all detergents are non-biodegradable; branched alkylbenzene sulfonates are the problematic ones.
- Classifying antiseptics and disinfectants as interchangeable.
- Assuming antibiotics work against viruses.