15.1 The representation of polymers is based on the use of “repeated groups”, i.e. sequences of identical groups. These groups are abbreviated [X]n in square brackets, where n is the number of times that they appear.
15.2 Repeated groups are either “monomers”, i.e. “normal” structural formulae, or “repeated structural units”, which are relatively complex multivalent radicals.
15.3 The normal formulae, i.e. those of the relevant monomers, are used when it is difficult to specify how the monomers are bonded, or in order to show simple oligomers with a maximum of eight repeated groups:
15.4 By and large, polymers are depicted as repeated structural units in which terminal bonds are shown. In linear polymers, such units are bivalent radicals:
poly (methyl methacrylate)
This also applies to polymers when the terminal groups are shown:
15.5 Network polymers can be shown by multivalent repeated structural units:
15.6 The representation of copolymers depends on what is known about the bonding of the constituent monomers. Thus normal formulae are used when it is difficult to specify the way in which the monomers are bonded:
Repeated structural units are used when the atoms involved in bonding are defined. The bonds are represented as unbroken lines between the monomers when their positions are known, but they are shown as unattached when the way in which the monomers are linked has not been precisely determined:
copolymers of ethene and vinyl ethanoate (acetate) (EVA)
15.7 Sequences of polymers are shown in a similar way: