Chemistry Reference
In-Depth Information
CHAPTER 8
Copolymers and Interpenetrating
Networks
8.1 RANDOM COPOLYMERS
Random copolymers are prepared by the copolymerization of a mixture of
cyclic oligomers.
1-5
Although the resulting polymer can be quite blocky
(figure 8.1), taking the reaction to equilibrium can give a polymer that is
essentially random in its chemical sequencing.
4,
6
One reason for prepar-
ing copolymers is to introduce functional species, such as hydrogen or
vinyl side groups, along the chain backbone to facilitate cross linking. An-
other reason is the introduction of sufficient chain irregularity to make
the polymer inherently noncrystallizable.
Specific examples of comonomers include imides,
7-12
perylenediimide,
13
urethane-ureas,
14,
15
epoxies,
16 -19
other siloxanes,
20-23
amides,
24
styrene,
25
divinylbenzene,
26
acrylics,
27, 28
silsesquioxanes,
29
polythiophenes,
30
and
poly(lactic acid).
31
One novel combination is the preparation of polysiloxane-
based episulfide resins.
32
An unusual application is the use of monomethyl-
itaconate-grafted polymethylsiloxane to induce crystal growth of CaCO
3
.
33
Polysiloxanes containing thermally curable brenzoxazine moieties in the
main chain are also in the category.
34
These and other copolymers have been extensively characterized by nu-
clear magnetic resonance (NMR) spectroscopy.
35
8.2 BLOCK COPOLYMERS
The sequential coupling of functionally terminated chains of different
chemical structure can be used to make block copolymers,
36,
37
including
