Imidazoles, ring-opening polymerization

A similar class of siloxane polymers was created with imi-dazolium groups (Cl5). ° Monomer synthesis consisted of combining N-allylimidazole and methyldiethoxysilane at elevated temperature. Homopolymers were created by polycondensation. Polymers with dimethylsiloxane spacers were also created by anionic ring-opening polymerization. Both classes of imidazole polymers were then reacted with n-octyl bromide to create the imidazolium side chains. Bactericidal activities of these polymers were similar to the quaternary ammonium polymers. 

Scheme 11 Imidazole catalyzed functionalization of starch via ring opening polymerization of 8-caprolactone. ...

Imidazole is a well-known initiator for the anionic ring-opening polymerization of epoxides. The photogeneration of imidazole and its subsequent use as an initiator for the polymerization of multifunctional epoxy-novolak resins have been reported by Nishikubo et Photolysis of the nitro-benzyl derivative 119 as shown in Scheme 36 generates imidazole, 120, which forms zwitterionic intermediate, 121, by reaction with the epoxide. The latter species is a rather weak nucleophile and the application of heat (120 °C) was required to drive the polymerization to completion. 

Another curing mechanism is operative in the curing reaction initiated by a polymerization catalyst for epoxy ring opening, where anionic catalysts such as tertiary amines 1S-l9) and imidazols 20 21> and cationic catalysts such as amine complexes of... 

Keywords cyclooctene, homogeneous catalysis, imidazole, ortto-metallation, ring-opening metathesis polymerization (ROMP), triazole... 

The mechanism of homopolymerization of epoxy resins initiated by imidazoles is now well established. A first nucleophilic attack by the unsubstituted nitrogen atom of the imidazole ring forms zwitterion 57 (Fig. 7, path C), which rearranges to an adduct by internal proton transfer. This is followed by a nucleophilic reaction of the newly formed unsubstituted nitrogen, opening a second epoxy group to give the 2 1 adduct that promotes the anionic polymerization of the epoxy. FTIR... 

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