Solution

Natural rubber, polypropylene and polythene polymerize by chain-growth polymerization of isoprene (2-methyl-1,3-butadiene), propylene and ethene, respectively.

Chain-growth polymerization (or addition polymerization) involves the linking together of molecules incorporating double or triple carbon-carbon bonds.

Terylene polymerizes by step-growth polymerization, in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long-chain polymers. Terylene is formed by ethylene glycol and terephthalic acid.