Chemistry Reference
In-Depth Information
The five general classes of polymers can be defined as
1. Homopolymers, in which all the monomer units are identical.
2. Heteropolymers or random copolymers, in which at least two different
monomer units are arranged in a more-or-less random manner along the chain.
3. Block and graft or comb copolymers, in which different monomer units are
linked in homogeneous groups to make up the chain or different monomer
units are grafted onto a main chain or backbone to form a comblike structure.
4. Polyelectrolytes, which can be members of any of the three classes above, but
with the characteristic that they carry a significant number of electrical
charges along the chain that impart special characteristics to the class.
Schematic representations of the five classes are shown in Figure 7.1. The represen-
tations given are intended to be illustrative and in no way show the true complexity
of most polymer chains. The polymers structures illustrated in the figure are gen-
erally synthetic, but natural polymers can also fall into the same categories.
Polymers such as cellulose, starches, natural gums, acrylates, acrylamides, poly-
ethyleneimines, and pyrollidones have been staples of the water-soluble polymer
industry for many years. In an attempt to expand the basic utility of such materials,
and to solve certain technological needs not satisfied by more conventional amphi-
philic materials, they have been modified to give special performance additives in
Figure 7.1.
Schematic representations of the five general classes of polymers, where A,B,C
represent different monomer units.
