Structure-reactivity relationships polymerization

A discussion of this polymerization method would not be complete without mention of the development of specialized glassware utilized over the years. It has evolved from very elaborate, sophisticated, and specially designed glassware to fairly simple setups. Initially, elaborate break-seal technology was used to complete the entire polymerization process,143 similar to anionic polymerization methodology.17 Break-seal techniques were employed to fully understand many monomer structure-reactivity relationships these techniques are no longer needed. 

Ni catalysts for olefin polymerization incorporating a-iminocarboxamide ligands are activated by the formation of borane-carbonyl adducts (153).542 Structure/reactivity relationships are similar to Brookhart s dimine catalysts. 

Radical polymerization is the most useful method for a large-scale preparation of various kinds of vinyl polymers. More than 70 % of vinyl polymers (i. e. more than 50 % of all plastics) are produced by the radical polymerization process industrially, because this method has a large number of advantages arising from the characteristics of intermediate free-radicals for vinyl polymer synthesis beyond ionic and coordination polymerizations, e.g., high polymerization and copolymerization reactivities of many varieties of vinyl monomers, especially of the monomers with polar and unprotected functional groups, a simple procedure for polymerizations, excellent reproducibility of the polymerization reaction due to tolerance to impurities, facile prediction of the polymerization reactions from the accumulated data of the elementary reaction mechanisms and of the monomer structure-reactivity relationships, utilization of water as a reaction medium, and so on. 

Our approach was to study structure reactivity relationships in a number of model reactions and, then, to proceed to the usually more difficult polymerizations using a variety of comonomer pairs. Secondly, we hoped to optimize the various, experimental solid-liquid PTC parameters such as nature and amount of catalyst, solvent, nature of the solid phase base, and the presence of trace water in the liquid organic phase. Finally, we wished to elucidate the mechanism of the PTC process and to probe the generality of solid-liquid PTC catalysis as a useful synthetic method for polycondensation. 

Crucially, discrete Ln/Al organometallics were unambiguously identified as intermediates of the commercially applied neodymium-based diene polymerization and subsequently employed in binary initiator mixtures. Particularly for the industrially relevant O-only bonded carboxylate- and alk(aryl)oxide rare-earth metal components, the use of pre-alkylated Ln derivatives developed into valuable structure-reactivity relationships partially uncovering the blackbox, which is provided by ternary Ziegler Misch-katalysatoren. Accordingly, rare-earth metal centers provide a unique stereo-... 

The ADMET step condensation polymerization of carbosila- and carbosiloxa-dienes has generated a new class of unsaturated silicon-containing polymers when monomer structure/reactivity relationships, as described earher for the polar functionalities, are obeyed (equation 22). 

Development of the elucidation of the catalytic reaction mechanism and the structure-reactivity relationships proceeded much more slowly. By the mid-1960s Wilke [17], Porri [18], and Dolgoplosk [19] had already shown that allyl-transition metal complexes can catalyze the butadiene polymerization stereoselectively and quite probably represent the real catalysts. In particular the allylnickel(II) complexes [Ni(C3Hs)X]2 (X = I [20], CF3CO2 [21]) and more recently the cationic complexes [Ni(C3H5)L2]PFe, with L = P(OPh)3, etc. [22, 23], were also used to explore the catalytic reaction mechanism. 

The mechanism of stereoregulation, however, remained unclear for many years. Only more recently has an experimentally well-founded comprehensive reaction model been derived for the allylnickel complex-catalyzed 1,4-polymerization of butadiene, which convincingly explains the catalytic reaction mechanisms and the structure-reactivity relationships also involving the industrial nickel catalyst [26-28]. 

Structure-Reactivity Relationships in Ring-Opening Polymerization... 

Concurrent with the development of the mechanistic explanations for the chemistry has been the creation of new polymers based on ROMP chemistry. While a wide variety of strained cyclic monomers have been polymerized with a significant emphasis on monomer structure/reactivity relationships, three ring structures deserve special attention, since they are or have been produced on a commercial scale. These polymers are polyoctenamer (from cyclooctene), polynorbornene (from... 

This article is primarily concerned with chain copolymerization. Chain copol5nner-ization is important as it allows a wide array of functional molecules to he designed and incorporated into pol5mieric materials. In addition, fundamental studies on copolymerization allow the mapping out of monomer structure-reactivity relationships that imderpin our knowledge of polymerization reaction mechanisms. 

Tsuruta, T. Structure-reactivity relationship of catalysts for ring-opening polymerization of some oxiranes. Pure Appl. Chem. 1981,55,1745-1751. 

Styrene Transfer reactions were also evidenced with borohydride precatalysts associated to BEM in styrene polymerization. In a study centered around the structure/reactivity relationships of the precatalyst, it was shown that Ln(BH4)3(THF)j x = 3, Ln = Nd, La) as well as the mixed La(BH4)2Cl(THF)2g led to an efficient transmetalation of the growing polystyrene chain with the Mg-CTA (Scheme 27.5). However, NMR and MALDI-TOF studies established the simultaneous occurrence of some fi-W abstraction. Such uncontrolled termination reactions were absent with LaCl3(THF)3,... 

Degirmenci Isa, Avci Duygu, and Aviyente Viktorya K. Density functional theory study of free-radical polymerization of acrylates and methacrylates Structure-reactivity relationship. Macromolecules. 40 no. 26 (2007) 9590-9602. 

Yang, F.-Z., Chen, Y.-C., Lin, Y.-F. et al. (2009) Nickel catalysts bearing bidentate a-aminoaldimines for ethylene polymerization—independent and cooperative structure/reactivity relationship resulting from unsymmetric square planar coordination. Dalton Transactions, 1243-1250. 

The a-fiinctionalization of polymer chains can be readily performed by using an appropriate initiator, bearing the functionalized fragment on the alkyl moiety (Table 4). Gigmes et al prepared a large number of alkoxyamines with various functionalized alkyl moieties for structure-reactivity relationships studies but only a few of them were used for polymerization purpose. 

Structure-Reactivity Relationships Based on a Comprehensive Survey of the Current Literature 333 Table 13.1 Anionic polymerization of electrophilic cyclopropanes. 

Structure and Reactivity Relationships in the Photoinitiated Cationic Polymerization of 3,4-Epoxy cyclohexylmethyl-3, 4 -epoxy cyclohexane... 

Cationic polymerizations induced by thermally and photochemically latent N-benzyl and IV-alkoxy pyridinium salts, respectively, are reviewed. IV-Benzyl pyridinium salts with a wide range of substituents of phenyl, benzylic carbon and pyridine moiety act as thermally latent catalysts to initiate the cationic polymerization of various monomers. Their initiation activities were evaluated with the emphasis on the structure-activity relationship. The mechanisms of photoinitiation by direct and indirect sensitization of IV-alkoxy pyridinium salts are presented. The indirect action can be based on electron transfer reactions between pyridinium salt and (a) photochemically generated free radicals, (b) photoexcited sensitizer, and (c) electron rich compounds in the photoexcited charge transfer complexes. IV-Alkoxy pyridinium salts also participate in ascorbate assisted redox reactions to generate reactive species capable of initiating cationic polymerization. The application of pyridinium salts to the synthesis of block copolymers of monomers polymerizable with different mechanisms are described. 

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