Catalyzed chain growth

The first report of catalyzed chain growth on aluminum was presented by Samsel et al., using metallocenes of actinides [13] or hafnium [14, 15], Gibson et al. described a detailed study of chain growth using the bis(imino)pyridyl iron complex 1 in combination with several metal alkyls [16], Other systems reported to... 

From the data and accompanying analysis in a study of catalyzed chain growth polymerization of diethylzinc and n-alkene synthesis , we deduce that the reaction 2... 

Biopolymers are naturally occurring polymers that are formed in nature during the growth cycles of all organisms they are also referred to as natural polymersJ Their synthesis generally involves enzyme-catalyzed, chain growth polymerization reactions, typically performed within cells by metabolic processes. 

Biopolymers are polymers formed in nature during the growth cycles of all organisms hence, they are also referred to as natural polymers. The biopolymers of interest in this review are those that serve in nature as either structural or reserve cellular materials. Their syntheses always involve enzyme-catalyzed, chain-growth polymerization reactions of activated monomers, which are generally formed within the cells by complex metabolic processes. The most prevalent structural and reserve biopolymers are the polysaccharides, of which many different types exist, but several other more limited types of polymers exist in nature which serve these roles and are of particular interest for materials applications. The latter include the polyesters and proteins produced by bacteria and the hydrocarbon elastomers produced by plants (e.g. natural rubber). In almost all cases (natural rubber is an exception), all of the repeating units of these biopolymers contain one or more chiral centers and the repeating units are always present in optically pure form that is, biopolymers with asymmetric centers are always 100% isotactic. 

Kinetic studies on the dissociation of AlfCHsls from [Cp2M(/r-CH3)2Al(CH3)2] [B(C5H5)4] (M = Ti, Zr, Hf) have been conducted in an effort to provide insight into the mechanism of transfer of alkyl groups from M to Al. Transfer is expected to occur when Zr, for example, is used to catalyze chain growth in aluminum alkyls and when Zr is used to catalyze carboalumination of olefins. The catalytically active species is thought to be a coordinatively unsaturated cationic species Cp2Zr" -CH3, which can be trapped by aluminum alkyls to form the adduct, shown ... 

Although Ni(0)-arene r-complexes have been characterized [37] and impHcated as intermediates in oxidative addition [38] and cross-coupling [39], there is at present no direct evidence of its intermediacy in the Ni-catalyzed chain-growth polymerization. Kiriy indirectly probed the existence of a 7r-complex by examining whether the chain-growth mechanism was affected by monomer length [26e]. A decrease in chain-growth behavior for terthiophene was observed compared to bithiophene... 

Miyakoshi, R., A. Yokoyama, and T. Yokozawa. 2005. Catalyst-transfer polycondensation mechanism of Ni-catalyzed chain-growth polymerization leading to well-defined poly(3-hexylthiophene). JAm Chem Soc 127 (49) 17542-17547. 

Scheme 27.10 Analogy between lanthanidocene-mediated polyethylene catalyzed chain growth (CCG) and half-lanthanidocene-mediated polystyrene CCG.

There are only a few reports on the ROP of lactides that do not use organometallic promoters. The synthesis of biomacromolecules generally involves in vivo enzyme-catalyzed chain growth polymerization reactions within cells. Enzymes exhibit high, stereo-, reaction- and substrate... 

Lanni EL, McNeil AJ (2009) Mechanistic studies on Ni(dppe)C12-catalyzed chain-growth polymerizations evidence for rate-determining reductive elimination. J Am Chem Soc... 

Lanni EL, McNeil AJ (2010) Evidence for ligand-dependent mechanistic changes in nickel-catalyzed chain-growth polymerizations. Macromolecules 43 8039-8044... 

Lanni EL, Locke JR, Cleave CM, McNeil AJ (2011) Ligand-based steric effects in Ni-Catalyzed chain-growth polymerizations using bis(dialkylphosphino)ethanes. Macromolecules 44 5136-5145... 

Enz5mie-catalyzed chain growth potymerization reactions of activated monomers are general involved in the synthesis of natural polymers, which are usualty formed within cells by complex metabolic process. 

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