Captodative olefins in polymer chemistry

Abstract

The radical polymerization behavior of captodative olefins such as acrylonitriles, acrylates, and acrylamides m-substituted by an electron-donating substituent is reviewed, including the initiated and spontaneous radical homo-and copolymerizations and the radical polymerizations in the presence of Lewis acids. The formation of low-molecular weight products under some experimental conditions is also reviewed. The reactivity of these olefins is analyzed in the context of the captodative theory. In spite of the unusual stabilization of the captodative radical, the reactivity pattern of these olefins in polymerization does not differ signifcantly from the pattern observed for other 1,1-disubstituted olefins. Classical explanations such as steric effects and aggregation of monomers are sufficient to rationalize the observations described in the literature. The spontaneous polymerization of acrylates e-substituted by an ether, a thioether, or an acylamido group can be rationalized by the Bond-Forming Initiation theory.

Die Verwendung von Lewis-Säuren bei Reaktionen freier Radikale

“…[4] So wurde zum Beispiel festgestellt, daû die Homopolymerisation von Acrylnitril und Methylmethacrylat durch die Zugabe von ZnCl 2 beschleunigt wird, und auch bei Copolymerisationen wurden überraschende Ergebnisse erhalten: [5] In Abwesenheit von Lewis-Säuren werden regelmäûige, alternierende Polymere nur aus solchen Monomerenpaaren gebildet, die aus einem starken Elektronenacceptor und aus einem starken Elektronendonor bestehen. Monomere mit weniger stark ausgeprägten Donor/ Acceptor-Eigenschaften führten zu Polymeren von nur mäûiger Alternanz.…”

“…[16] Ohne (4) aktions-artige Addition von Bromtrichlormethan an 9 führt durch Addition an C5 hauptsächlich zum Produkt 10 a (10 a:10 b 74:26). Werden Lewis-Säuren wie Ti(OiPr) 2 Cl 2 zugesetzt, kehrt sich die Regioselektivität um, und 10 b wird zum Hauptprodukt der Reaktion (10 b:10 a 26:74).…”

Use of Lewis Acids in Free Radical Reactions

“…[4] For example, it has been observed that homopolymerization of acrylonitrile and methyl methacrylate could be enhanced by the addition of ZnCl 2 and very important effects have been observed in Use of Lewis Acids in Free Radical Reactions Philippe Renaud* and Miche Á le Gerster After a long period of neglect, radical chemistry has been investigated seriously, and exciting new developments have been reported. [4] For example, it has been observed that homopolymerization of acrylonitrile and methyl methacrylate could be enhanced by the addition of ZnCl 2 and very important effects have been observed in Use of Lewis Acids in Free Radical Reactions Philippe Renaud* and Miche Á le Gerster After a long period of neglect, radical chemistry has been investigated seriously, and exciting new developments have been reported.…”

“…10b 9 (4) from the addition at C5 (10 a:10 b 74:26). In the presence of Lewis acids such as Ti(OiPr) 2 Cl 2 the regioselectivity is inverted and 10 b is the major product of the reaction (10 b:10 a 26:74).…”

Radical Polymerization of Methyl Methacrylate by Captodative Substituted Morpholino Succinonitrile

“…In the copolymerizations of various cd substituted olefins amino groups serve as a stronger electron-donating substituent. 12 Therefore, cd ethanes substituted by amino moiety can be expected to dissociate at higher rates due to stronger cd stabilization of the dissociated radical to give a labile domant although the cd stabilization effect originates basically from the synergistic interaction between electron-withdrawing and -donating moieties and the dissociation rate is also influenced by steric hinderance of an ethane.…”