Polymeric metal

In the early 1950s, Ziegler observed that certain heterogeneous catalysts based on transition metals polymerized ethylene to a linear, high density material at modest pressures and temperatures. Natta showed that these catalysts also could produce highly stereospecific poly-a-olefins, notably isotactic polypropylene, and polydienes. They shared the 1963 Nobel Prize in chemistry for their work. 

Dental alloys and metals. Polymeric dental materials. Abrasives,... 

The conjugated stmcture of 1,3-butadiene gives it the abiUty to accept nucleophiles at both ends and distribute charge at both carbon 2 and 4. The initial addition of nucleophiles leads to transition states of TT-ahyl complexes in both anionic and transition-metal polymerizations. 

Single-crystal samples of conductors best other solid samples are suitable, including polycrystalline metals, polymeric materials, semiconductors, and insulators, ultrahigh vacuum compatible typically > 5 mm diameter, 1-3 mm thick... 

Bipyridines were efficiently used in supramolecular chemistry [104], Since the molecule is symmetric no directed coupling procedure is possible. In addition, 2,2 6/,2//-terpyridine ligands can lead to several metal complexes, usually bis-complexes having octahedral coordination geometries [105,106], Lifetimes of the metal-polymeric ligand depend to a great extent on the metal ion used. Highly labile complexes as well as inert metal complexes have been reported. The latter case is very important since the complexes can be treated as conventional polymers, while the supramolecular interaction remains present as a dormant switch. 

Transition metal polymerization catalysts have stimulated tremendous efforts in academic research resulting in numerous industrial applications. Ziegler-Natta and metallocene catalysts have been used for the synthesis of tailor-... 

Several important classes of polar monomers have so far eluded copolymerization by the Pd(II) system. Vinyl chloride insertion, for example, leads to catalyst deactivation following P-halide elimination to form inert chloride species such as 1.32, as shown by Jordan [90], Similarly, attempted vinyl acetate copolymerization results in deactivation by an analogous acetate elimination process, although the ester chelate intermediate that forms after insertion also effectively shuts down the reaction [90], Therefore, -elimination of polar groups represents a significant and unresolved problem for late transition metal polymerization systems unless access of the metal to it is restricted. 

Fig. 11 Late transition metal polymerization catalysts from cyclic a-diimine ligands...

The recent progress surveyed in this review shows the promise that late transition metal catalysts can provide in the production of new materials. We will continue our exploration of new catalyst design for the synthesis of new functional materials with unconventional topologies. Given the unique features of late transition-metal polymerization catalysts and further improvement in catalyst stability and activity for copolymerization with polar comonomers, the future of designing novel functional polymeric materials with late-transition-metal catalysts is very promising. 

Luinstra GA, Queisser J, Bildstein B, Gortz H, Amort C, Malaun M, Krajete A, Weme G, Kristen MO, Huber N, Gernert C (2003) In Striegler S (ed) Late transition metal polymerization catalysis. Wiley-VCH, Weinheim, pp 59-99... 

Late Transition Metal Polymerization Catalysis. Rieger, B. Saunders, L. Kacker, S. Striegler, S. Eds. 2003, Wiley-VCH Verlag GmbH, Weinheim, Germany. 

The general issues from literature surveys dealing with lanthanide initiators reveal the following (1) catalyst precursors with larger lanthanide metals polymerize lactide faster than metals of smaller radii, (2) lanthanide catalysts polymerize lactide at slower rates than cyclic esters such as s-caprolactone and, in most cases. 

Lehman, S. E., Jr. and K. B. Wagener, Macromolecules, 35, 702 (2002) Catalysis in ADMET Polymerizations, Chap. 6 in Late Transition Metal Polymerization Catalysis, B. Rieger, L. Baugh, S. Kacker, and S. Striegler, eds., Wiley-VCH, New York, 2003. 

The calculated transition state for -hydrogen transfer (Fig. 3) has a non-planar 6-membered ring structure. There is no direct interaction between the aluminium atom and the hydrogen being transferred. Thus, the situation differs sharply from that for transition metal polymerization, where the transition state has some resemblance to a hydride-bis(olefin) complex, as illustrated for a typical metallocene case in Fig. 3. 

In the following sections, we describe the recent development of catalyst systems for epoxide polymerization, focusing on homopolymerization, (alternating) co-polymerization with CO or GO2 reported from 1993 to 2004. Although aluminum and zinc are not classified as transition metals, polymerization catalyst systems using those metals will be discussed since they greatly contribute to the field of epoxide polymerization. 

Moore, J. S. Transition Metals in Polymer Synthesis Ring-opening Metathesis Polymerization and Other Transition Metal Polymerization Techniques. In Comprehensive Organometaltic Chemistry // Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds. Elsevier Oxford, 1995 Vol. 12, pp 1209-1232. 

When metal atoms condense on a surface, the recombination to form bulk metal will occur at a rate controlled only by diffusion even at 4 K. Thus, any desired atom-molecule reaction occurring on cocondensation must be very facile to compete with metal polymerization. 

A comparison of Figs. 5 and 6 shows that between the anionic polymerization of styrene and the transition metal polymerization of styrene there is a region of poor catalysts which produce either atactic or no polymers. It has been shown by the substitution effects of the reaction that both the styryl anion and the styryl cation propagate on the... 

The reverse reaction of oxidation of the metal or reduction of the moiety is also known to occur in stereospecific catalyst systems. It has been long known that the polymerization of olefine materials can be accomplished in non-alkyl systems. Diem, Tucker and Gibbs (43) have shown that the lithium metal polymerization of isoprene proceeds with the initial reduction by the electron seeking lithium of the nucleophilic diene to produce the corresponding alkyl lithium. Fukui, Schimidzu, Yagi, Fukumoto, Kagiya and Yuosa (127) have studied the polymeriza-... 

Consiglio, G. (2003) in Late Transition Metal Polymerization Catalysis... 

A few other pertinent observations have been made. Although the effect of temperature on structure in the case of sodium or potassium metal polymerized butadiene was shown to lead to the gradual approach to a nearly random mixture between 0 and 45° (41,32), in the case of phenyllithium in tetrahydrofuran there is observed only a few percent difference between — 78° and + 100° (76). Furthermore, the use of lithium, n-butyllithium, n-amyllithium or isoamyllithium produces polyisoprene of the same microstructure in tetrahydrofuran (77). Kuntz (34) found that polybutadiene prepared with n-butyllithium in... 

With the help of complementary surface analysis techniques such as XPS, Static SIMS and AES, we have been able to show how a short (23 msfilms leads to a slight oxidation of the surface as well as to the formation of N2 containing species. These modifications are necessary for the improvement of the adhesion observed with a scotch-tape test. However, the presence of oxygen is not the only factor responsible for a good adhesion, since the AES profiles of die deposited aluminium, show the same oxidized interface in the case of the non treated metallized polymeric film. The films are pretreated in a corona discharge configuration (hollow electrode-grounded cylinder) and the aluminium is deposited onto the film in situ. 

Unlike early transition metal polymerization catalysts which do not tolerate functional groups, cationic palladium complexes are able to copolymerize ethylene with methyl acrylate.128... 

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