Chemistry Reference
In-Depth Information
This limitation to the definition will become clearer in context when some of these
polymer types, like alkyds (
Section 1.6
), are discussed later in the text. Any defi-
ciency in the general application of the term is not serious, since the concept of a
repeating unit is in fact only employed where such groupings of atoms are readily
apparent.
1.1.5
Representations of Polymer Structures
Polymer structures are normally drawn as follows by showing only one repeating
unit. Each representation below is equivalent to the corresponding structure that
has been depicted above:
H
polystyrene
CH
2
C
x
1-1a
poly(ethylene terephthalate)
O
CH
2
CH
2
O
C
C
n
O
O
1-5a
H
H
poly(hexamethylene adipamide)
N
CH
2
NC
CH
24
C
i
6
O
O
1-6a
H
poly(vinyl alcohol)
CH
2
C
OH
m
1-8a
The subscripts x, n, i, m, and so on represent the number of repeating units in
the polymer molecule. This number is often not known definitely in commercial
synthetic polymer samples, for reasons which are explained later in the text.
