Ziegler polymerization

Ziegler polymerization catalysts may be prepared from Cp—Zr complexes and tri alkyl aluminum. The molecular weight of the polymers can be controlled over a wide range by varying the temperature. The activity of these catalysts is considerably increased by the addition of small amounts of water (263,264) (see Olefin polya rs). 

The preparation and characterization of 1,3-butadiene monomer is discussed extensively elsewhere (1 4) (see Butadiene). Butadiene monomer can be purified by a variety of techniques. The technique used depends on the source of the butadiene and on the polymerization technique to be employed. Emulsion polymerization, which is used to make amorphous /n j -l,4-polybutadiene (75% trans-1 4 , 5% kj -l,4 20% 1,2), is unaffected by impurities during polymerization. However, both anionic and Ziegler polymerizations, which are used to prepare kj -l,4-polybutadiene, mixed cis-1 4 and... 

Wilke s allyl compounds were found to be very poor catalysts indeed, e.g., Ti(2 Me-allyl)4, was found only to have an activity equal to 0.5 gm/m.M Ti/atm/C2H4/hr. For this reason there has been considerable dispute that transition metal alkyls can be the intermediates in Ziegler polymerization. 

The Ziegler polymerizations of olefins (92, 5) and the aluminum (108), gallium, beryllium, and indium (ill) alkyl growth reactions also seem to be examples of olefin insertion reactions of metal-carbon compounds. Despite great effort concerning the mechanism of the polymerization reactions, relatively little has been learned about the actual catalytic species involved. 

The report of Bestian Clauss that methyltitanium trichloride will undergo a slow growth reaction with ethylene in polar inert solvents at low temperatures (6) is considerably important because of its relation to the Ziegler polymerization reaction. 

Anionic polymerization of conjugated dienes and olefins retains its lithium on the chain ends as being active moities and capable of propagating additional monomer. This distinguishing feature has an advantage over other methods of polymerization such as radical, cationic and Ziegler polymerization. Many attempts have been made to prepare block copolymers by the above methods, but they were not successful in preparing the clear characterized block copolymer produced by anionic technique. 

Apel , is obtained by Ziegler polymerization. It is available in film and resin form. The material exhibits a high density and a bulky structure. It is amorphous, optically isotropic and non polar (70). Topas is copolymerized from norbornene and ethylene using a metallocene catalyst. 

The straight-chain alcohol used for this ester is known commercially as Alfol 610 and is produced by the Ziegler polymerization of ethylene. The composition of the alcohol is 20% Ce. 35% Cs. and 44% C10. 

This evidence supports the concept that the Ziegler polymerization of styrene is by catalysts with cationicities which lie between the cationic Friedel-Crafts system and the anionic alkyl sodium system. Its character can be shifted depending on the ratio of the aluminum to titanium. 

This reaction was described by Gibson et al. 441 and the properties of the polymer have been reviewed 45>. Ziegler polymerization gives the cyclopolymer as a soluble... 

Since 1961, the industrial importance of the hydroformylation reaction has been threatened by newer processes (19) such as the Ziegler polymerization of ethylene, the Wacker process, and the direct oxidation of petroleum (153). The industrial aspects of the Oxo reaction were reviewed in 1965 when the world production capacity for Oxo products was estimated at 0.5 million tons per year (39). 

In spite of some declining industrial interest, the last 5 years have seen an unusual academic interest in the catalytic properties of the metal carbonyls. This has been part of a wider surge of interest in the organometallic chemistry of the transition metals and its application to homogeneous catalysis. Reactions such as Ziegler polymerization, the Oxo reaction, and the Wacker process are but a few of the many reactions of unsaturated molecules catalyzed in the coordination sphere of transition metal complexes (20). These coordination catalyses have much in common, and the study of one is often pertinent to the study of the others. 

Derivation Benzene is alkylated with dodecene, to which it attaches itself in any secondary position the resulting dodecylbenzene is sulfonated with sulfuric acid and neutralized with caustic soda. For ABS (branched-chain alkyl) the dodecene is usually a propylene tetramer, made by catalytic polymerization of propylene. For LAS (straight-chain alkyl), the dodecene may be removed from kerosene or crudes by molecular sieve, may be formed by Ziegler polymerization of ethylene, or by cracking wax paraffins to a-olefins. 

Use Ziegler polymerization catalyst (with aluminum alkyls). 

The mechanism by which Ziegler polymerizations proceed has been the subject of investigation and speculation ever since Ziegler s discovery. The numerous theories that have been proposed fall in general into two classes ... 

Fr . 1. Mechanisms of Ziegler polymerization (a) Bimetallic mechanism, (b) Monometallic mechanism [after Cossee]. (c) Monometallic Cossec mechanism (5). Crystal structure of a-TiC. la with active center in the surface. A propylene rnolocule is inserted in the Cl v acancy forming a 7r-bond with Ti ion A. Figures lb and Ic wore reprinted with the permission of the Faraday Society. 

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