Copoly vinylamine/4 -vinylimidazole

A summary of our recent publications describing water-soluble imidazole containing pol3rmers is presented. Copoly[l-alkyl-4- or 5-vinylimidazole/4(5)-vinylimidazolej (I), copoly[vinylamine/4(5)-vinyl-imidazole] (II), and dodecane-block-poly[ethylen-imine-graft-4(5)-methylimidazole] (III) have been used to investigate the hydrophobic interaction in esterolytic reactions. A brief survey of related work is presented along with our current work. 

This review article summarizes our more recent investigations of the esterolytic action of water soluble imidazole containing polymers. In our previous work we have explained increased reactivity of polymeric reactants in terms of electrostatic and cooperative effects. Recently, we have directed our efforts in emphasizing the apolar interaction as it has reflected dramatic rate enhancements and proven a predominant factor in determining the maximum catalytic efficiency. Polymeric catalysts which are included in this review are poly[l-alkyl-4(5)-vinyl-imidazoles] and their copolymers, hydro-phobic terpolymers of 4(5)-vinylimidazole, copoly[vinylamine/4(5)-vinylimidazole], and poly(ethylenimine-g L-histidine). All of these catalysts share the common property of water solubility and the capability of attaining high catalytic efficiencies which is attributed to apolar interactions. 

Copoly[vinylamine/4(5)-vinylimidazole] extends the studies of poly[4(5)-vinylimidazole] catalyzed ester hydrolysis to an aqueous environment. Copoly[vinylamine/4(5) vinylimidazole] were prepared as shown in Scheme III. 

Copolymerization of 4(5)-vinylimidazole with vinylamine increased the water solubility of the catalyst and, therefore its esterolytic activity.(15) Copoly[4(5)-vinylimidazole-vinylamine] (II) had considerably lower pKa values for the imidazole residues in water (5.11-5.40) than the imidazole residues for PVIm in 28.5% ethanol-water (5.78-6.20).(14) Apart from the difference in solvent, the polyelectrolyte effect from the strongly basic amine residues (pKa 7.35-7.74 in water) was responsible for the lower pKa values. 

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