The Influence of the Nature of the Catalytic System on Zirconocene‐Catalyzed Polymerization of Alkyl Methacrylates

Abstract

Three non‐bridged dimethylzirconocene complexes; i.e., bis(η5‐cyclopentadienyl)dimethylzirconium (1), bis(η5‐tert‐butyl‐cyclopentadienyl)dimethylzirconium (2), bis(η5‐indenyl)dimethylzirconium (3), and the chiral zirconocene rac‐ethylenebis(η5‐indenyl)dimethylzirconium (4) were synthesized and used as catalysts for the polymerization of methyl methacrylate, MMA, combined with tris(pentafluorophenyl)borate (A) or tetrakis(pentafluorophenyl)borate dimethylanilinum salt (B) in the presence of ZnEt2. The evolution of the polymerization characteristics; i.e., molecular weight, molecular‐weight distribution, and yield were examined for the above systems. The influence of the nature of the solvent was also investigated. The aggregation behavior, the steric hindrance, and the lipophilicity of the active catalytic systems are the most important parameters determining the polymerization characteristics. The tacticity of the products is reported and the influence of the catalyst structure is discussed. Finally, the polymerization of other methacrylates (alkyl = butyl, hexyl, decyl, stearyl, and sec‐butyl), was conducted and the effect of the nature of the alkyl ester group on the molecular and structural characteristics was established.

Polymerization of higher α‐olefins using a Cs‐symmetry hafnium metallocene catalyst. Kinetics of the polymerization and microstructural analysis

“…This period is devoted for the activation of the catalyst by the cocatalyst and the complexation of the first monomer unit for the initiation of the polymerization process. This behavior was reported earlier for the polymerization of hexene‐1 with zirconocenes20 and also for the polymerization of other monomers as well 21. After this period the molecular weight and the yield increase linearly with time.…”

“…The less aggregated the active centers the higher is the acceleration of the polymerization reaction. In polar solvents the enhanced ion separation reduces the degree of aggregation leading to higher polymerization activities 21, 26. The same effect can be observed using bulky monomers.…”

Catalytic Activity Dependency on Catalyst Components in Aerobic Copper–TEMPO Oxidation

“…The controlled polymerization of methyl methacrylate (MMA) by metallocenes such as zirconocenes1–12 and lanthanocenes13–21 has been well documented. A neutral metallocene enolate or a cationic zirconocene enolate is believed to participate in the propagation with a propagating mechanism analogous to group‐transfer polymerization 22, 23.…”

Controlled vinyl‐type polymerization of norbornene with a Nickel(II) diphosphinoamine/methylaluminoxane catalytic system

“…In particular, the active centers, formed in situ by the interaction between the catalyst and MAO cocatalyst, consist of alkyl metal cations attended by weakly coordinated counter anions. For catalytic systems such as the one under investigation, MAO anions are in general relegated to the second coordination sphere, rendering the ion pairs more ionic, thereby allowing for the formation of aggregates in nonpolar solvents 40–42. The extent of aggregation is mainly determined by two factors: The first is the steric hindrance introduced by the ligands of the catalysts; the bulkier the ligands the lower the aggregation number.…”