Copolymerization of ethene with norbornene and functionalized norbornenes in
both non-aqueous and aqueous solutions could be carried out by (salicylaldimino)
nickel methyl complexes [114, 123–125], square-planar nickel complexes containing
anionic P,O-chelates [126], and by Pd phosphine aryl sulfonates [127–129].
Bazan reported on the synthesis of pseudo-tetrablock copolymers comprised of
ethene and 5-norbornen-2-yl acetate, using the initiator system (LiPr 2 )Ni(η
1
–CH 2 Ph)
(PMe 3 ) [(LiPr 2 ) ¼ N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)
propanamide] and 2.5 equivalents of Ni(cod) 2 [bis(1,5-cyclooctadiene)nickel
[121, 130, 131]. Square-planar nickel complexes with anionic P,O-chelate ligands
were used by Goodall and coworkers for the co- and terpolymerization of
norbornene and 5-norbornene-2-carboxylic acid ethyl ester with ethene [126].
Also, complexes IX-2–IX-3 with 2,6-lutidine and pyridine as neutral ligand,
were demonstrated to act as single-component catalysts for the copolymerization of
ethene with norbornene derivatives N OH and N AC , yielding comparable results to
phosphine-based analogues apart from the molar mass distribution, which was
evidently affected by a less-efficient activation [122].
The well-defined complex [Pd(κ 2 -P,O-{2-(2-MeOC 6 H 4 ) 2 P}C 6 H 4 SO 3 )Me(dmso)]
(X-1), having dimethylsulfoxide (dmso) as labile ligand, was investigated as a
single-component catalyst for the copolymerization of ethylene with norbornene,
affording P(E-co-N) in excellent yields and with molar masses significantly higher
than those of polyethylene. Copolymer molar masses increased with norbornene
concentration and reached values that are interesting for industrial applications.
Such an increase, along with the presence of only terminal vinyl groups in the
1 H
NMR spectra of copolymers, revealed that norbornene limits β-H elimination and
thus both chain walking and chain termination. The more labile dmso, with respect
to the pyridine in Claverie catalyst (X-2) due the more facile activation, leads to
higher activities in E-co-N copolymerization. The use of the well-defined catalyst
rather than the in-situ generated one leads to higher activity and a better control of
copolymerization in terms of norbornene incorporation. Determination of microstructure and reactivity ratios revealed a strong inherent tendency to form
alternating copolymers [129].
X-1 copolymerizes ethene with N OH and N AC . In the case of 5-norbornene-2-yl
acetate, the activity and molar masses resemble those of E-co-N copolymerization.
6 Other Cycloolefin Copolymers
A drawback of E–N copolymers endowed with high T g values is their brittleness at
high norbornene content. The substitution of norbornene with a bulkier cycloolefin
monomer could result in a more ductile COC by obtaining the same T g values at a
lower amount of cycloolefin content and thus copolymers with a higher amount of
flexible ethene units in the chain. The properties of a COC based on bicyclic
monomers can be varied by varying the norbornene content or the structure of
the bicycloolefin; this includes norbornadiene, dicyclopentadiene (DCPD),
Polyolefins with Cyclic Comonomers
135
both non-aqueous and aqueous solutions could be carried out by (salicylaldimino)
nickel methyl complexes [114, 123–125], square-planar nickel complexes containing
anionic P,O-chelates [126], and by Pd phosphine aryl sulfonates [127–129].
Bazan reported on the synthesis of pseudo-tetrablock copolymers comprised of
ethene and 5-norbornen-2-yl acetate, using the initiator system (LiPr 2 )Ni(η
1
–CH 2 Ph)
(PMe 3 ) [(LiPr 2 ) ¼ N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)
propanamide] and 2.5 equivalents of Ni(cod) 2 [bis(1,5-cyclooctadiene)nickel
[121, 130, 131]. Square-planar nickel complexes with anionic P,O-chelate ligands
were used by Goodall and coworkers for the co- and terpolymerization of
norbornene and 5-norbornene-2-carboxylic acid ethyl ester with ethene [126].
Also, complexes IX-2–IX-3 with 2,6-lutidine and pyridine as neutral ligand,
were demonstrated to act as single-component catalysts for the copolymerization of
ethene with norbornene derivatives N OH and N AC , yielding comparable results to
phosphine-based analogues apart from the molar mass distribution, which was
evidently affected by a less-efficient activation [122].
The well-defined complex [Pd(κ 2 -P,O-{2-(2-MeOC 6 H 4 ) 2 P}C 6 H 4 SO 3 )Me(dmso)]
(X-1), having dimethylsulfoxide (dmso) as labile ligand, was investigated as a
single-component catalyst for the copolymerization of ethylene with norbornene,
affording P(E-co-N) in excellent yields and with molar masses significantly higher
than those of polyethylene. Copolymer molar masses increased with norbornene
concentration and reached values that are interesting for industrial applications.
Such an increase, along with the presence of only terminal vinyl groups in the
1 H
NMR spectra of copolymers, revealed that norbornene limits β-H elimination and
thus both chain walking and chain termination. The more labile dmso, with respect
to the pyridine in Claverie catalyst (X-2) due the more facile activation, leads to
higher activities in E-co-N copolymerization. The use of the well-defined catalyst
rather than the in-situ generated one leads to higher activity and a better control of
copolymerization in terms of norbornene incorporation. Determination of microstructure and reactivity ratios revealed a strong inherent tendency to form
alternating copolymers [129].
X-1 copolymerizes ethene with N OH and N AC . In the case of 5-norbornene-2-yl
acetate, the activity and molar masses resemble those of E-co-N copolymerization.
6 Other Cycloolefin Copolymers
A drawback of E–N copolymers endowed with high T g values is their brittleness at
high norbornene content. The substitution of norbornene with a bulkier cycloolefin
monomer could result in a more ductile COC by obtaining the same T g values at a
lower amount of cycloolefin content and thus copolymers with a higher amount of
flexible ethene units in the chain. The properties of a COC based on bicyclic
monomers can be varied by varying the norbornene content or the structure of
the bicycloolefin; this includes norbornadiene, dicyclopentadiene (DCPD),
Polyolefins with Cyclic Comonomers
135