Vinylimidazole-acrylic acid copolymers

So far, many kinds of nucleophiles active for hydrolysis such as imidazolyl-, amino-, pyridino-, carboxyl- and thiol-groups, have been used for preparation of hydrolase models. Overberger et al.108,1091 prepared copolymers of vinylimidazole and acrylic acid 60 (PVIm AA), by which the cationic substrate, 61 (ANTI), was hydrolyzed. This kind of copolymer is considered to be a model of acetylcholinesterase. With ANTI, the rate of the copolymer catalysis was higher than that of imidazole itself in the higher values of pH, as is seen in Table 9. In this work, important contributions of the electrostatic interactions are clear. The activity of the copolymer was not as high with the negatively charged and neutral substrates. 

The same technique can be used to dye a material that is otherwise difficult to dye. An ethylene-propylene copolymer rubber was reacted first with maleic anhydride, then with an aromatic amine dye in an extruder to produce a dyed rubber.81 Dye sites can also be inserted into polyolefins by grafting them with dimethylaminoethyl methacrylate, using azo or peroxide catalysts in an extruder.82 jV-Vinylimidazole has been grafted to polyethylene in an extruder with the help of dicumylperoxide.83 The product was mixed with an acrylic acid-modified polypropylene and used to compatibilize polyethylene and polypropylene. This could be helpful in the recycling of mixed polyolefins from municipal solid waste. Recycling of cross-linked (thermoset) polymers is more of a problem because they cannot be remelted in an extruder. However, they can be if... 

SSlimidzu et al. 83) also studied the c ytic solvolysis by copolymers of vinylimidazole and acrylic acid. The Michaelis-Menten type behavior was observed for the solvolysis of ANTI 32 but not for that of PNPA 3 in 100% aqueous systems, in contrast to the second-order kinetic behavior in 28.5% ethanol-water as reported by Overberger et al. 80). Substrate binding as given by 1/Am fias maximal at 25 to 30 mol% imidazole content, and the intracomplex rate for the neutral imidazole unit was minimal at 20 to 30 mol% imidazole contents. The resulting overall efficiency simply decreased with increasing imidazole contents. 

Compatibilized blends of ethylene-methacrylic acid copolymer and PS were prepared by Kim et al. (1998) through addition of S-co-4-vinylpyridine. Similarly, blends of poly(isobutyl methacrylate) were compatibilized with poly(styrene-co-methacrylic acid) using poly(isobutyl methacrylate-co-2-(A, A -dimethylamino) ethyl methacrylate) or poly(isobutyl methacrylate-co-4-vinylpyridine) (Habi and Djadoun 1999). Turcsayii (1995) has reported compatibilized blends of PE-g-(N-vinylimidazole) with acrylic acid-modified PP. 

The copolymer of A -vinylimidazole and acrylic acid has been found to be an effective esterolytic catalyst for the hydrolysis of p-nitrophenyl acetate (Letsinger and Klaus, 1964 Shimidzu et al., 1974). The carboxyl groups in this polymer can bind a positively charged substrate, e.g. (3). Thus, the catalytic esterolytic activity of such a polymer for the positively charged 3, the neutral 4 and the negatively charged 5 is in the order ... 

The cooperative interaction between imidazole and carboxylic groups was also investigated by Overberger and his collaborators. They looked at the solvolysis of 3-acetoxy-A -trimethylanilinium iodide (ANTI) catalyzed by a polymer of 4(5)-vinylimidazole and acrylic acid (see Figure 3). More recently, Overberger et al [16] have investigated the effect of copolymers containing imidazole and mercaptan functions upon ester hydrolysis. 

Shimidzu etal.111 studied the catalytic activity of poly (4(5)-vinylimidazole-co-acrylic add) 60 (PVIm AA) in hydrolyses of 3-acetoxy-N-trimethylanilinium iodide 61 (ANTI) and p-nitrophenylacetate 44 (PNPA). The hydrolyses of ANTI followed the Michaelis-Menten-type kinetics, and that of PNPA followed the second-order kinetics. Substrate-binding with the copolymer was strongest at an imidazole content of 30 mol%. The authors concluded that the carboxylic acid moiety not... 

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