the polyolefin pendant chain originating from 7-octenyl-Si(CH 3 ) 2 Ph comonomer
was effective and offered new possibilities for post-functionalization. In these
approaches it has been possible to convert pendant groups in PE-co-SiPh and
PP-co-SiPh to reactive fluorine, chlorine, methoxy, and ethoxysilane groups. In
addition, hydrosilylation post-reactions were also investigated. Thus, synthesized
reactive polyolefins have been shown to perform excellently as compatibilizers in
polymer blends and composites [25–29].
2 Copolymerization Behavior of Bis(indenyl) Metallocenes
This section reviews copolymerization studies and aims to give an overview of
research on ethylene-1-olefin copolymerization, the role of ligand substitution in
copolymerization and the polymerization mechanisms involved. The copolymerization behavior of a group of siloxy-substituted complexes is discussed because
they have the ability to be activated at low MAO ratios and some of them provide
excellent comonomer response.
Scheme 1 displays metallocenes discussed in this paper. Table 1 summarizes
selected literature data regarding ethylene reactivity ratios (r E ) in ethylene/1-olefin
copolymerization.
Ligand substitution, transition metal (Ti, Zr, Hf), and the interannular bridge
have distinctive effects on the copolymerization behavior. Electronic factors at the
active site and the steric environment in the vicinity of the active site of a
metallocene catalyst determine the reactivity of monomers and the structure of
the copolymer. Many general conclusions about the influence of the ligand structure
on the polymer structure [30] can be made, although the details of how the
combination of electronic and steric effects determines the reactivities of reactants
are not fully understood. General conclusions are the following:
• Substitution of Cp ligand decreases comonomer response [31]
• Bridged metallocene complexes have better comonomer response than
non-bridged metallocenes
• Indenyl ligand substituted metallocenes have higher comonomer intake than
tetrahydroindenyl ligand substituted ones
• Dimethyl silyl bridge improves comonomer response over ethyl bridge
• Hf complexes have higher comonomer reactivity than Zr analogues [32]
• Half metallocenes have typically high comonomer response but no stereo
control
• Meso complexes have substantially higher comonomer response than their
racemic counter parts
• Siloxy-substitution at 3-position significantly improves reactivity towards
comonomer
• 4-Phenyl or benz[e]indenyl substitution further improves comonomer response
184
J. Seppa ¨la ¨ et al.
was effective and offered new possibilities for post-functionalization. In these
approaches it has been possible to convert pendant groups in PE-co-SiPh and
PP-co-SiPh to reactive fluorine, chlorine, methoxy, and ethoxysilane groups. In
addition, hydrosilylation post-reactions were also investigated. Thus, synthesized
reactive polyolefins have been shown to perform excellently as compatibilizers in
polymer blends and composites [25–29].
2 Copolymerization Behavior of Bis(indenyl) Metallocenes
This section reviews copolymerization studies and aims to give an overview of
research on ethylene-1-olefin copolymerization, the role of ligand substitution in
copolymerization and the polymerization mechanisms involved. The copolymerization behavior of a group of siloxy-substituted complexes is discussed because
they have the ability to be activated at low MAO ratios and some of them provide
excellent comonomer response.
Scheme 1 displays metallocenes discussed in this paper. Table 1 summarizes
selected literature data regarding ethylene reactivity ratios (r E ) in ethylene/1-olefin
copolymerization.
Ligand substitution, transition metal (Ti, Zr, Hf), and the interannular bridge
have distinctive effects on the copolymerization behavior. Electronic factors at the
active site and the steric environment in the vicinity of the active site of a
metallocene catalyst determine the reactivity of monomers and the structure of
the copolymer. Many general conclusions about the influence of the ligand structure
on the polymer structure [30] can be made, although the details of how the
combination of electronic and steric effects determines the reactivities of reactants
are not fully understood. General conclusions are the following:
• Substitution of Cp ligand decreases comonomer response [31]
• Bridged metallocene complexes have better comonomer response than
non-bridged metallocenes
• Indenyl ligand substituted metallocenes have higher comonomer intake than
tetrahydroindenyl ligand substituted ones
• Dimethyl silyl bridge improves comonomer response over ethyl bridge
• Hf complexes have higher comonomer reactivity than Zr analogues [32]
• Half metallocenes have typically high comonomer response but no stereo
control
• Meso complexes have substantially higher comonomer response than their
racemic counter parts
• Siloxy-substitution at 3-position significantly improves reactivity towards
comonomer
• 4-Phenyl or benz[e]indenyl substitution further improves comonomer response
184
J. Seppa ¨la ¨ et al.