Recent examples for synthesis of group 4 transition metal (Ti, Zr, Hf) complexes, especially nonbridged half-metallocenes containing anionic donor ligands of the type, Cp′MX 2 (L) (Cp′ = cyclopentadienyl group; M = Ti, Zr, Hf; X = halogen, alkyl etc.; L = anionic donor ligands), as catalysts for precise olefin polymerization have been reviewed. It has been revealed that these complex catalysts displayed unique characteristics especially for ethylene copolymerizations and some examples are known to produce new polyolefins that cannot be prepared by ordinary catalysts such as classical Ziegler–Natta, metallocenes. Modification of both cyclopentadienyl fragment and anionic ancillary donor ligands are the key for precise olefin (co)polymerization.

Nonbridged half-metallocenes containing anionic ancillary donor ligands: New promising candidates as catalysts for precise olefin polymerization

Organometallic catalysts for copolymerization of cyclic olefins

Metallocene catalyzed ethene- and propene co-norbornene polymerization: Mechanisms from a detailed microstructural analysis

The copolymerization of ethene with norbornene derivatives, as well as their terpolymerization with 1-alkenes, using a series of neutral, square-planar nickel complexes containing anionic P∼O chelates is described. In copolymerizations, up to 50 mol % incorporation of norbornene, leading to an essentially alternating copolymer, is obtained. With norbornene derivatives bearing oxygen functionalities, the level of incorporation is lower, as are the reaction rates and polymer molecular weights. In the case of terpolymerization of ethene and norbornene with 1-alkenes, the polymer molecular weights tend to be low because of slower monomer insertion and additional chain-transfer pathways that are available following 1-alkene insertion. For the ethene/norbornene polymers synthesized, the glass transition temperature (Tg) increases smoothly with increasing norbornene content. Solution-cast films of the polymers show good optical clarity.

Copolymerization of Ethene with Norbornene Derivatives Using Neutral Nickel Catalysts

Ethylene−norbornene (E−N) copolymers were synthesized by catalytic systems composed of racemic isospecific metallocene or a constrained geometry catalyst (CGC) and methylaluminoxane. The following ...

Ethylene−Norbornene Copolymers from Metallocene-Based Catalysts: Microstructure at Tetrad Level and Reactivity Ratios

This study involves research on possible relationships between the composition of ethylene/norbornene copolymers and their thermal properties. The copolymers were fully characterised by differential scanning calorimetry (DSC), 13 C NMR spectroscopy, Fourier transformation infra-red (FTIR) and Raman spectroscopy. The results of this study show that there is no linear correlation between the amount of norbornene incorporated in copolymers and thermal behaviour when copolymers containing high norbornene content and different microstructures are considered. The latter of which was found to be extremely sensitive to the catalyst used in its preparation.

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Influence of the polymer microstructure on the thermal properties of cycloolefin copolymers with high norbornene contents

A range of ethylene/norbornene copolymers were synthesized using the commercially available rac-Et(Ind)2ZrCl2 metallocene catalyst. A large window of norbornene contents, between 30 and 55 mol % was used to facilitate the interpretation of the results. The polymers were characterized by means of wide-angle X-ray scattering, differential scanning calorimetry, and dynamic mechanical thermal analysis. The X-ray diffractograms showed two amorphous halos, the low-angle one increasing in the intensity with norbornene content. Calorimetric and dynamic mechanical results led to a linear relation between the glass transition temperature and the norbornene content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2159–2165, 2001

Thermal and dynamic mechanical behavior of ethylene/norbornene copolymers with medium norbornene contents

Various tri- and tetracyclic olefinic hydrocarbons were polymerized via ring-opening metathesis polymerization (ROMP) initiated by different molybdenum carbene complexes. The influence of molecular weight and microstructure on the glass transition temperature of obtained polymers were investigated. Molecular weights were regulated by addition of 1-octene as a chain-transfer agent. The content of cis vinylene units in the polymer backbone was varied by using molybdenum carbenes with various alkoxy groups. Furthermore the effects of different bicyclic units in the polymer backbone on the glass transition temperature were investigated. Polymers were characterized by FT-IR, NMR and size exclusion chromatography (SEC) using calibration vs. polystyrene standards, differential viscosity and light scattering.

Influence of microstructure on properties of polymers with high glass transition temperatures obtained by ring-opening metathesis polymerization of polycyclic hydrocarbons

High strength steel in marine environments suffers from severe corrosion susceptibility and the presence of bacteria can exacerbate the effect, accelerating degradation via microbiologically influenced corrosion (MIC). Here we propose a novel approach to MIC inhibition by designing a system capable of limiting the effects of both bacterial growth and corrosion. The combination of a newly synthesised compound, cetrimonium 4-hydroxycinnamate (Cet-4OHCin), with lanthanum 4-hydroxycinnamate was the only system tested to date that could both inhibit abiotic corrosion in artificial seawater and minimise bacteria consortium densities over an exposure period of 24 h. This success was proposed to be due to them having the same anion, making them stable when mixed in the solution of the test environment. Furthermore, we confirmed from cytotoxicity testing that Cet-4OHCin demonstrated similarly limited toxicity towards human cells as the commercially available cetrimonium bromide, a known safe additive to cosmetic products. This new system shows promise as a safe and effective multifunctional inhibitor mixture to reduce the effects of MIC. 

John Forsyth

Papers

Influence of the polymer microstructure on the thermal properties of cycloolefin copolymers with high norbornene contents

Thermal and dynamic mechanical behavior of ethylene/norbornene copolymers with medium norbornene contents

Influence of microstructure on properties of polymers with high glass transition temperatures obtained by ring-opening metathesis polymerization of polycyclic hydrocarbons

Inhibitor mixture for reducing bacteria growth and corrosion on marine steel†