Chemistry Reference
In-Depth Information
H
O
H
O
N
N
+
N
H
N
N
n
O
O
H
When in place of succinimide a cyclic carbonate is used, a high molecular weight polyurethane
forms [
210
]:
H
H
O
N
NO
+
O
N
N
n
O
O
H
Terpolymers form from epoxides, anhydrides, and tetrahydrofuran or oxetane with a
trialkylaluminum catalyst [
211
]:
O
O
+
O
+
O
O
O
O
O
n
O
O
Copolymerizations of caprolactone with caprolactam in various ratios take place with lithium
tetraalkylaluminate as the catalyst [
212
]. The products are mainly random copolymers with some
block homopolymers.
When lactones copolymerize with cyclic ethers, such as
-propiolactone with tetrahydrofuran, in
the early steps of the reaction the cyclic ethers polymerize almost exclusively [
213
]. This is due to the
greater basicity of the ethers. When the concentration of the cyclic ethers is depleted to equilibrium
value, their consumption decreases markedly. Polymerizations of the lactams commence. The
products are block copolymer [
213
].
b
5.15 Spontaneous Alternating Zwitterion Copolymerizations
This type of copolymerization results from spontaneous interactions of nucleophilic and electrophilic
monomers (M
N
and M
E
, respectively) without any additions of catalysts. Zwitterions form in the
process that subsequently leads to formation of polymers [
214
-
226
]. The mechanism is a step-growth
polymerization. It can be illustrated as follows:
M
N
+
M
N
M
E
M
E
M
N
M
N
M
E
M
N
M
E
M
E
M
N
M
E
+
M
N
M
E
M
N
M
E
+
M
N
M
E
M
N
M
E
M
N
M
E
etc.
2
