Chemistry Reference
In-Depth Information
For instance, polymerization of norbornene with a tungsten based catalyst, combined with (C
2
H
5
)
3
Al as
the co-catalyst,
Ph
Ph
O
Cl
O
NW
O
Cl
78
C, 92%
was reported to have yielded at
polymer [
173
].
Nevertheless, the Grubbs catalysts are very versatile and have made a great impact on polymer
chemistry. Following are additional examples of use of Grubbs catalysts. One of them is ruthenium
catalysts based on [RuCl
2
(arene)] dimers, with ligands of durene or
cis
-cymene. They were formed by
addition of tricyclohexylphosphine and activatedwith (trimethylsilyl)diazomethane [
174
]. These catalysts
showgood functional compatibility in preparationof a variety of polyoctenamerswith epoxide, acid, ether,
ester, acetal and bromine functionalities.
236
The following illustration serves as an example [
174
]:
p
P
Ru
H
H
H
Ru
P
O
O
O
n
O
In addition, it was shown that some ring-opening metathesis polymerizations exhibit the
characteristics of living polymerizations. Thus, the polymerization of cyclobutene with a tungsten
catalyst [W(CH-
2,6-diisopropyllphenyl), was shown to fit the
category of living polymerization and was used to form block copolymers [
175
,
176
]. Similarly,
some substituted cyclobutanes were polymerized in a living manner using a molybdenum catalyst,
Mo(CHC(CH
3
)
2
Ph)(NAr)(OC(CH
3
)
2
CF
3
)
2
t
-C
4
H
9
)(NAr)(
O
-
t
-C
4
H
9
)
2
] (Ar
¼
2,6-diisopropylphenyl] in combination with
PPhMe
2
[
177
]. Also, bicyclo[3.4.0]heptene polymerization was found to be a living one when a
ruthenium catalyst, (PPh
3
)
2
Cl
2
Ru
[Ar
¼
CPh
2
was used [
178
].
Formation of block copolymers with pendant carbazole groups was reported via a living ring-opening
metathesis polymerization using a ruthenium catalyst [
179
]. In addition, what appears to be a first
example of a homogeneous living polymerization in water was reported recently [
180
]. The reaction
was carried out in the presence of a Bronsted acid using alkylidine ruthenium complexes. Water-
soluble monomers polymerized quickly and quantitatively in the absence of surfactants or organic
solvents. These polymerizations were found not to be living, however, when the Bronsted acid was
absent [
180
]. It was suggested that the function of the acid is to eliminate hydroxide ions and to
enhance the catalyst activity by protonating the phosphine ligands [2180].
Yong and Swager [
181
] reported ring-openingmetathesis copolymerizations of calixarene containing
monomers with cyclooctene and norbornene to yield highmolecular weight transparent elastic polymers.
Pitet and Hillmyer [
182
] combined metathesis ring-opening polymerization with cyclic ester ring-
openingmetathesis polymerization to form triblock AABA copolymers of cycloocatadiene and
D
,
L
-lactide.
¼
CHCH
¼
