Chemistry Reference
In-Depth Information
Some other reactions of the epoxy groups are [
99
]:
O
HO
O
CH
2
Cl
ClCH
2
COOH
HO
Cl
O
HO
Cl
HOH
piperidine
OH
HO
HO
N
9.3 Rearrangement Reactions
There are different types of polymeric rearrangements. One of them is isomerizations of polymers
with double bonds. Others can be intramolecular cyclizations in the polymeric backbone.
9.3.1
Isomerization Reactions
cis
The isomerization of
-polybutadiene can be carried out with the aid of ultraviolet light or with
gamma radiation. When light is used, the free-radical reaction requires photoinitiators [
102
,
103
].
The mechanism involves freely rotating transitory free-radicals on the polymer backbone. These form
from additions of photoinitiator fragments to the double bonds. The adducts break up again, releasing
the attached initiator fragments and reestablishing the double bonds. The new configurations are
trans
because they are more thermodynamically stable [
102
,
103
]. This can be shown as follows:
X
X
X
+
cis
