Chemistry Reference
In-Depth Information
H
H
H
H
~ CH
2
C
CH
2
C
CH
2
C
CH
2
C ~
1-1
Polymers generally have molecular weights greater than about 5000 but no
firm lower limit need be defined since the meaning of the word is nearly always
clear from its use. The word macromolecule is a synonym for polymer.
1.1.2
Monomer
A monomer is a molecule that combines with other molecules of the same or dif-
ferent type to form a polymer. Acrylonitrile, CH
2
Q
CHCN, is the monomer for
polyacrylonitrile:
H
H
H
H
~ CH
2
C
CH
2
C
CH
2
C
CH
2
C ~
CN
CN
CN
CN
1-2
which is the basic constituent of “acrylic” fibers.
1.1.3
Oligomer
An oligomer is a low-molecular-weight polymer. It contains at least two monomer
units. Hexatriacontane (n-CH
3
—(CH
2
)
29
—CH
3
) is an oligomer of polyethylene
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
:
1-3
Generally speaking, a species will be called polymeric if articles made from it
have significant mechanical strength and oligomeric if such articles are not strong
enough to be practically useful. The distinction between the sizes of oligomers
and the corresponding polymers is left vague, however, because there is no sharp
transition in most properties of interest.
The terms used above stem from Greek roots: meros (part), poly (many), oligo
(few), and mono (one).
