7 Conclusions
Norbornene polymerization is the most versatile of the cycloolefin addition
polymerizations. Single-site catalysts such as metallocene compounds, constrained
geometry catalysts (CGCs), and nickel or palladium diimine complexes, used in
combination with MAO or borate cocatalysts, are active for the copolymerization of
norbornene with ethene. The structure of the norbornene homo- and copolymers
can be widely influenced by the symmetry and structure of the ligands on the
transition metal complexes.
Commercial ethene–norbornene copolymer products obtained using early
transition metal catalysts are already available. E–N copolymers are usually
amorphous and display a wide range of T g , from room temperature to about
220
C. They are characterized by high chemical resistance and good processability
[39]. They show excellent transparency and high refractive index owing to their
high carbon/hydrogen ratio, e.g., the refractive index is 1.53 for a 50:50 E–N
copolymer. These properties make them suitable for optical applications such as
coatings for high-capacity CDs and DVDs, for lenses, medical equipment, blisters,
toner binder, and packaging. During the last two decades, progress in metallocene
catalysts for cycloolefin copolymerization has made possible the commercialization
of E–N copolymers. A commercial plant for the production of COC material (E–N
copolymer) was built in 2000 by Ticona in Oberhausen, Germany, with a capacity
of 30,000 tons per annum. Mitsui produces E–N copolymers using vanadium-based
catalysts. The industrially produced copolymers have norbornene contents of
between 30 and 60 mol% and T g values of 120–180
C. The copolymer densities
are low and near 1. For many applications, these COC materials show better
mechanical properties than comparable amorphous thermoplastics and are processable by all conventional methods.
By contrast, copolymerizations of norbornene with higher α-olefins or styrenes
and conjugated dienes, or of polycycloolefins, still give low activity, low comonomer incorporation, and low molar masses. Thus, synthesis of new organometallic complexes with various metal centers and with ancillary ligands with
appropriate structure will play an important role for their controlled copolymerization, which can lead to COC with desired physical, mechanical, and optical
properties.
Late transition metal catalysts, which are more tolerant of polar functional
groups than early transition metal catalysts, are most suitable and highly active
for norbornene homopolymerizations or copolymerization with other cycloolefins.
A range of tailor-made homo-, co-, and terpolymers based on substituted
norbornenes for applications in electronic materials are produced and
commercialized, but they need further development to be efficiently used in
olefin–cycloolefin copolymerizations.
Polyolefins with Cyclic Comonomers
137
Norbornene polymerization is the most versatile of the cycloolefin addition
polymerizations. Single-site catalysts such as metallocene compounds, constrained
geometry catalysts (CGCs), and nickel or palladium diimine complexes, used in
combination with MAO or borate cocatalysts, are active for the copolymerization of
norbornene with ethene. The structure of the norbornene homo- and copolymers
can be widely influenced by the symmetry and structure of the ligands on the
transition metal complexes.
Commercial ethene–norbornene copolymer products obtained using early
transition metal catalysts are already available. E–N copolymers are usually
amorphous and display a wide range of T g , from room temperature to about
220
C. They are characterized by high chemical resistance and good processability
[39]. They show excellent transparency and high refractive index owing to their
high carbon/hydrogen ratio, e.g., the refractive index is 1.53 for a 50:50 E–N
copolymer. These properties make them suitable for optical applications such as
coatings for high-capacity CDs and DVDs, for lenses, medical equipment, blisters,
toner binder, and packaging. During the last two decades, progress in metallocene
catalysts for cycloolefin copolymerization has made possible the commercialization
of E–N copolymers. A commercial plant for the production of COC material (E–N
copolymer) was built in 2000 by Ticona in Oberhausen, Germany, with a capacity
of 30,000 tons per annum. Mitsui produces E–N copolymers using vanadium-based
catalysts. The industrially produced copolymers have norbornene contents of
between 30 and 60 mol% and T g values of 120–180
C. The copolymer densities
are low and near 1. For many applications, these COC materials show better
mechanical properties than comparable amorphous thermoplastics and are processable by all conventional methods.
By contrast, copolymerizations of norbornene with higher α-olefins or styrenes
and conjugated dienes, or of polycycloolefins, still give low activity, low comonomer incorporation, and low molar masses. Thus, synthesis of new organometallic complexes with various metal centers and with ancillary ligands with
appropriate structure will play an important role for their controlled copolymerization, which can lead to COC with desired physical, mechanical, and optical
properties.
Late transition metal catalysts, which are more tolerant of polar functional
groups than early transition metal catalysts, are most suitable and highly active
for norbornene homopolymerizations or copolymerization with other cycloolefins.
A range of tailor-made homo-, co-, and terpolymers based on substituted
norbornenes for applications in electronic materials are produced and
commercialized, but they need further development to be efficiently used in
olefin–cycloolefin copolymerizations.
Polyolefins with Cyclic Comonomers
137