Chemistry Reference
In-Depth Information
RO
N
RO
N
+
CT
+
N
N
donor
acceptor
cationic
polymerization
anionic
polymerization
where [CT] represents a charge transfer complex.
Solvation of the charged species accelerates the transfer of electrons and the ionizations are
enhanced by polar solvents [
57
]. Charge transfer reactions studies with tetracyanoethylene, an
acceptor, and
-vinylcarbazole, a donor, in benzene solution demonstrated that both cation-radicals
and anion-radicals form. This can be used in a subsequent cationic polymerizations [
60
]:
N
N
N
N
N
+
+
N
N
N
N
N
N
N
N
monomer
polymer
N
N
N
A similar reaction takes place between chloranil and
N
-vinyl carbazole [
61
]:
O
O
Cl
Cl
Cl
Cl
monom
er
+
polymer
CT
Cl
Cl
N
Cl
Cl
O
O
N
Alkyl vinyl ethers also polymerize in the presence of strong acceptors like tetracyanoben-
zoquinone, 2,3-dichloro-5,6-dicyano-
p
-benzoquinone, and tetracyanoethylene [
60
]. A similar reac-
tion mechanism was proposed [
60
].
Solutions of maleic anhydride in ether will initiate cationic polymerizations of isobutyl vinyl ether
or
N
-vinyl carbazole, if subjected to attacks be free radicals. The same is true if the solutions are
irradiated with ultraviolet light or gamma rays [
62
,
63
]. Also, active species are generated from
reactions of aldehydes or ketones with maleic anhydride when attacked by free radicals or irradiated
by UV-light, or gamma rays from
60
Co [
63
]. These active species are presumed to be formed through
charge-transfer reactions that occur between the electron acceptors,
p
-acids, or electron donors,
p
-
bases, which form cations [
64
].
