What is Polymer, monomer, polymerisation?

Example 49.7 (The monomer of PVC)

The chain $\ce{-CH2-CHCl-CH2-CHCl-CH2-CHCl-}$ repeats $\ce{-CH2-CHCl-}$; it holds only carbons in its main chain, so the monomer is $\ce{CH2=CHCl}$, chloroethene.

Example 49.8 (PET, a polyester)

Ethane-1,2-diol, $\ce{HO-CH2-CH2-OH}$, carries two alcohol groups; benzene-1,4-dicarboxylic acid, $\ce{HOOC-C6H4-COOH}$, two acid groups. Each acid group forms an ester with an alcohol group and releases water: the chain grows from both ends. The polymer is poly(ethylene terephthalate), PET, the material of drink bottles and of polyester fibres. Its repeat unit, $\ce{C10H8O4}$, has a molar mass of $192.0\,\mathrm{g}/\mathrm{mol}$, that is the two monomers ($62.0 + 166.0$) minus two molecules of water ($36.0$).

Example 49.9 (Nylon-6,6, a polyamide)

Hexane-1,6-diamine, $\ce{H2N-(CH2)6-NH2}$, and hexanedioic acid, $\ce{HOOC-(CH2)4-COOH}$, join by amide links, each releasing one molecule of water:

The two sixes in the name count the carbon atoms of each monomer. The amide links of neighbouring chains attract each other by hydrogen bonds, which makes nylon fibres strong.