Chemistry Reference
In-Depth Information
O
O
O
P
O
The opening of the phosphonium ring requires higher temperatures (above 120
C) and follows the
pattern of the Arbusov reaction [
224
,
226
]. Examples of some other monomers that can also act as
nucleophiles in the above reaction are
p
-formyl benzoic acid [
214
], acrylamide [
224
], and ethylene
sulfonamide. All three react in the same manner [
224
]:
O
O
NH
O
O
S
S
NH
2
+
P
P
O
O
O
O
O
O
P
O
O
S
n
NH
It is reasonable to expect that some compounds can act at one time as M
N
monomers and at other
times as M
E
, depending upon the comonomer. This is the case with salicylyl phenyl phosphonite
[
224
]. In the presence of bezoquinone it behaves as an M
N
monomer and produces a 1:1 alternating
copolymer at room temperature [
224
]:
O
X
X
O
X
X
P
O
O
+
OP
O
O
X
X
n
O
O
X
X
where, X
CN.
The above reaction is called a
redox copolymerization
reaction [
224
]. The trivalent phosphorus
in the monomer is oxidized to the pentavalent state in the process of polymerization and the quinone
structure is
¼
Y
¼
H; X
¼
Y
¼
Cl; X
¼
Y
¼
CH
3
;X
¼
Cl; and Y
¼
reduced to hydroquinone. The phosphonium-phenolate zwitterion is
the key
intermediate:
