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Industrial Polymers
Published in Manas Chanda, Plastics Technology Handbook, 2017
Despite the domination of supported catalysts in polyolefin production, industrial research work has shifted towards new generation, single-site, homogeneous, Ziegler–Natta catalyst systems, the main compound of which is the Group IVB transition metallocenes (titanocene, zirconocenes, and hafnocenes) [8]. The molecular structure of the two famous Brintzinger catalysts, ethylenebis (indenyl) zirconium dichloride Et(ind)2ZrCl2 and ethylenebis (tetrahydroindenyl) zirconium dichloride Et(H4Ind)2ZrCl2 are depicted in Figure 4.3. Methylalumoxane (MAO) is the most important co-catalyst that activates the group IVB metallocenes in homogeneous Ziegler–Natta polymerization.
Ionic Chain-Reaction and Complex Coordination Polymerization (Addition Polymerization)
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
While PP is often synthesized employing the ZNC, today there exist many other catalyst systems, including the soluble catalyst systems described in Section 5.6. Many of these were developed by Walter Kaminsky and coworkers in 1980. These catalysts contain a Group IVB metallocene coupled with methylaluminoxane (MAO). Through varying the structure of the metallocene cocatalyst, it is possible to tailor the tacticity of the product. Thus, for PP, the atactic product is formed when the simple zirconocene and hafnocene dichlorides are employed; syndiotactic PP is produced when a bridged catalyst is employed; and isotactic PP is produced when another bridged catalyst is employed.
Thermoplastic Elastomers
Published in Anil K. Bhowmick, Current Topics in ELASTOMERS RESEARCH, 2008
Francis R. Costa, Naba K. Dutta, Namita Roy Choudhury, Anil K. Bhowmick
TPEs can be obtained from many conventional homopolymerizing olefins, like propylene, ethylene, and 1-octene, using suitable metallocene catalyst or cocatalyst composition. A typical catalyst composition is metallocene of Ti, Zr, or Hf and methylaluminoxane (MAO) as cocatalyst. In this process, polymerization occurs along two propagation paths, wherein one path causes homopolymerization of the monomer stereoselectively into crystallizable blocks in the resulting polymer chain, and the other path creates irregular noncrystallizable amorphous blocks [88]. Tullock et al. [89] synthesized PP exhibiting elastomeric properties using bis(arene)Ti, Zr, and Hf catalyst with materials of heterogeneous composition. A complete review on propene-based elastomers by transition metal catalyst is available [90].
Zinc(II) complexes containing N′-aromatic group substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines: Synthesis, characterization, and polymerizations of methyl methacrylate and rac-lactide
Published in Journal of Coordination Chemistry, 2018
Sujin Shin, Hyungwoo Cho, Hyosun Lee, Saira Nayab, Younghak Kim
1H-pyrazole, para-formaldehyde, 3,5-dimethylaniline, 2,6-dimethylaniline, 2,6-diethylaniline, 2,6-diisopropylaniline, 4-bromoaniline, benzhydrylamine, magnesium sulfate (MgSO4), anhydrous [ZnCl2] and methyl methacrylate (MMA) were purchased from Sigma-Aldrich (St. Louis, MO) and anhydrous solvents, such as C2H5OH, DMF, hexane, and CH2Cl2 were purchased from Merck (Darmstadt, Germany) and used without further purification. Modified methylaluminoxane (MMAO) was purchased from Tosoh Finechem Corporation (Tokyo, Japan) as 5.9% aluminum (by weight) in a toluene solution and used without further purification. 1H-pyrazolyl-1-methanol, as starting material, was prepared according to the reported method [11]. The synthesis of LA − LE was carried out as reported previously [34–38].
Anchoring via covalent binding of a salicylaldimine-nickel complex in multi-walled carbon nanotubes and its application in ethylene oligomerization
Published in Journal of Coordination Chemistry, 2020
Cuiqin Li, Xue Zhai, Ming Cheng, Yang Li, Nian Li, Feng Li, Jun Wang
Multi-walled CNTs (>95%) (MWNTs) and 3-aminopropyl-trimethoxysilane were purchased from Sigma-Aldrich (Beijing, China). NiCl2·6H2O and salicylaldimine were obtained from Tianjin Guangfu Fine Chemical Research Institute (Tianjin, China). Methylaluminoxane (MAO, 10 wt% in toluene), diethylaluminum chloride (DEAC, 25 wt% in toluene), ethyl aluminum dichloride (EADC, 25 wt% in n-hexane), triethyl aluminum (TEAL, 25 wt% in n-hexane) and triethyldialuminum trichloride (EASC, 50 wt% in cyclohexane) were purchased from Sigma-Aldrich (China). All experiments were performed under a nitrogen atmosphere using standard Schlenk techniques, and all solvents were distilled by refluxing over sodium and benzophenone under nitrogen.
Synthesis and electronic structure of a series of first-row transition-metal pyrazine(diimine) complexes in two oxidation states
Published in Journal of Coordination Chemistry, 2022
Daniela Sanchez Arana, Jaylan R. Billups, Bruno Donnadieu, Sidney E. Creutz
Pyridine(diimine) iron dihalides have been widely studied and applied in catalysis. The ligand architecture has been heavily modified to tune the electronic properties of the overall complex by replacing the substituents on the imine phenyl rings or by controlling the bite angle of the pincer ligand, especially for use in ethylene polymerization reactions with MAO (methylaluminoxane) [36]. Several examples of low-valent iron pyridine(diimine) complexes have also been reported for the formation of new C–C and C–E bonds in hydrosilylation, hydroboration, and cycloaddition reactions [4, 37, 38].