Esterolytic activity of imidazole‐containing polymers. Synthesis and characterization of copoly[1‐alkyl‐4‐ or 5‐vinylimidazole/4(5)‐vinylimidazole] and its catalytic activity in the hydrolysis of p‐nitrophenyl acetate

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Abstract
The water‐soluble monomers, 1‐methyl‐4‐vinylimidazole, 1‐methyl‐5‐vinylimidazole, 1‐ethyl‐5‐vinylimidazole, and 1‐propyl‐5‐vinylimidazole have been synthesized, polymerized, and copolymerized with 4(5)‐vinylimidazole. The copolymers were characterized by 14C‐labeling, NMR, pKa determination and viscosity measurements. The monomer reactivity ratios determined by 14C counting are r1 = 1.04; r2 = 0.94 [M1 = 4(5)‐vinylimidazole, M2 = 1‐methyl‐4‐vinylimidazole] and r1 = 1.01; r2 = 0.86 [M1 = 4(5)‐vinylimidazole, M2 = 1‐methyl‐5‐vinylimidazole]. The esterolytic activity of the copolymers for the hydrolysis of p‐nitrophenyl acetate (PNPA) at pH 7–8 in 28.5% ethanol–water was higher than that of the mixtures of homopolymers. At pH 5–6 the esterolytic activities of the copolymers and the mixtures were similar. The most efficient esterolytic activity for PNPA hydrolysis at pH 7.11 in 28.5% ethanol–water occurred for copolymers containing 75 mole % 4(5)‐vinylimidazole and for copolymers containing 1‐methyl‐4‐vinylimidazole rather than 1‐methyl‐5‐vinylimidazole.

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