5 Copolymerization with Functionalized Norbornenes
The introduction of functional groups into cycloaliphatic polyolefin backbones
could allow significant control of surface properties such as adhesion, wettability,
dyeability, compatibility, and printability and could lead to COC with improved
properties. Catalysts based on Ni and Pd are intrinsically less sensitive to functional
groups than those based on the early transition metals currently employed in
industry [104].
Open late transition metal catalysts based on palladium salts and complexes are
highly active in norbornene homopolymerization in contrast to ansa-zirconocene
catalysts, which have low activity because of steric hindrance. After Sen [105]
reported on the dicationic system [CH 3 CN] 4 Pd[BF 4 ] 2 as a very active catalyst for
norbornene addition polymerization, Risse investigated the homo- and copolymerization of norbornene and its derivates (e.g., ester substituents) with Pd(II) catalysts
[106]. Goodall et al. recognized the potential of these polymers based on norbornene
derivatives and used highly active catalysts based on cationic or neutral nickel
and palladium complexes [107–109]. The homo- and copolymers of substituted
norbornenes obtained have high decomposition temperatures, small optical
birefringence, good transparency for short wavelength radiation, high plasma etch
resistance, and are suitable for advanced photoresist composition in microelectronic
industry. The palladium catalysts are less active than the nickel analogues. The
ligand structure does not influence the polymer microstructure and properties,
α-olefins act as chain transfer agents and allow control of the molecular weight.
Promerus produces a range of homo-, co-, and terpolymers based on substituted
norbornenes developed at BF Goodrich, such as Avatrel, Appear, and DUVCOR.
Brookhart breakthroughs [110] on late transition metals for olefin polymerization catalysts led to catalysts that allow incorporation of most polar functionalities.
For example, N^N Pd-based systems tolerate acrylates, vinyl ketones, and silyl
vinyl ethers, but they afford hyperbranched copolymers with functionalities located
mainly at the end of ramifications, while, Ni-based systems give linear copolymers
of ethene and methyl acrylate (MA) but with extremely low productivity. The
norbornene derivatives have the functional group distant from the double bond
and are more easily incorporated than functionalized α-olefins; however, a catalyst
for the copolymerization of ethene with functionalized norbornenes must be both
tolerant of functional groups and resistant to β-hydrogen elimination. Indeed, some
late transition metals are often ineffective for the copolymerization of ethene with
norbornene because 1-alkenes act as a chain transfer agent through β-hydrogen
elimination.
Kaminsky et al. succeeded in E–N copolymerizations by using α-diimine
palladium catalysts [111, 112]. The T g values of E–N copolymers produced are
very high and range from 98 to 217
C [111, 112]. Copolymers produced at
norbornene molar fraction (x N ) ! 0.80, as well as homo-polynorbornenes, show
no T g values or T m values under 350
C, and decompose above 350
C.
Polyolefins with Cyclic Comonomers
131
The introduction of functional groups into cycloaliphatic polyolefin backbones
could allow significant control of surface properties such as adhesion, wettability,
dyeability, compatibility, and printability and could lead to COC with improved
properties. Catalysts based on Ni and Pd are intrinsically less sensitive to functional
groups than those based on the early transition metals currently employed in
industry [104].
Open late transition metal catalysts based on palladium salts and complexes are
highly active in norbornene homopolymerization in contrast to ansa-zirconocene
catalysts, which have low activity because of steric hindrance. After Sen [105]
reported on the dicationic system [CH 3 CN] 4 Pd[BF 4 ] 2 as a very active catalyst for
norbornene addition polymerization, Risse investigated the homo- and copolymerization of norbornene and its derivates (e.g., ester substituents) with Pd(II) catalysts
[106]. Goodall et al. recognized the potential of these polymers based on norbornene
derivatives and used highly active catalysts based on cationic or neutral nickel
and palladium complexes [107–109]. The homo- and copolymers of substituted
norbornenes obtained have high decomposition temperatures, small optical
birefringence, good transparency for short wavelength radiation, high plasma etch
resistance, and are suitable for advanced photoresist composition in microelectronic
industry. The palladium catalysts are less active than the nickel analogues. The
ligand structure does not influence the polymer microstructure and properties,
α-olefins act as chain transfer agents and allow control of the molecular weight.
Promerus produces a range of homo-, co-, and terpolymers based on substituted
norbornenes developed at BF Goodrich, such as Avatrel, Appear, and DUVCOR.
Brookhart breakthroughs [110] on late transition metals for olefin polymerization catalysts led to catalysts that allow incorporation of most polar functionalities.
For example, N^N Pd-based systems tolerate acrylates, vinyl ketones, and silyl
vinyl ethers, but they afford hyperbranched copolymers with functionalities located
mainly at the end of ramifications, while, Ni-based systems give linear copolymers
of ethene and methyl acrylate (MA) but with extremely low productivity. The
norbornene derivatives have the functional group distant from the double bond
and are more easily incorporated than functionalized α-olefins; however, a catalyst
for the copolymerization of ethene with functionalized norbornenes must be both
tolerant of functional groups and resistant to β-hydrogen elimination. Indeed, some
late transition metals are often ineffective for the copolymerization of ethene with
norbornene because 1-alkenes act as a chain transfer agent through β-hydrogen
elimination.
Kaminsky et al. succeeded in E–N copolymerizations by using α-diimine
palladium catalysts [111, 112]. The T g values of E–N copolymers produced are
very high and range from 98 to 217
C [111, 112]. Copolymers produced at
norbornene molar fraction (x N ) ! 0.80, as well as homo-polynorbornenes, show
no T g values or T m values under 350
C, and decompose above 350
C.
Polyolefins with Cyclic Comonomers
131