Imidazole-containing polymers catalysis

In the area of catalysis, the esterolysis reactions of imidazole-containing polymers have been investigated in detail as possible models for histidine-containing hydrolytic enzymes such as a-chymotrypsin (77MI11104). Accelerations are observed in the rate of hydrolysis of esters such as 4-nitrophenyl acetate catalyzed by poly(4(5)-vinylimidazole) when compared with that found in the presence of imidazole itself. These results have been explained in terms of a cooperative or bifunctional interaction between neighboring imidazole functions (Scheme 19), although hydrophobic and electrostatic interactions may also contribute to the rate enhancements. Recently these interpretations, particularly that depicted in Scheme 19, have been seriously questioned (see Section 1.11.4.2.2). 

Catalysis by Water-Soluble Imidazole-Containing Polymers... 

The vinylphenol unit was similaily introduced to imidazole-containing copolymers cf. Section 4-4), but the incorporation resulted only in the increase of hydro-phobicity of the polymer catalyst On the other hand, some rate enhancements were observed due to phenolic compounds bound onto Bl-VP copolymers, and cooperative catalysis for die intraoanplex reactirxi was implied (71). 

Catalysis by Vinyl Polymers Containing Nudrofrfiiles Other than Imidazole... 

Interestingly, the 3 1 complex with the less symmetrical 3,4-substituted benzoic acid shows a more stable mesophase (K 79 M 244 I) than the derivative formed from the 3,4,5 substituted benzoic acid (K 63 M 214 I). A related system has also been reported which uses a benzotri(imidazole) (23) as the trifunctional core unit (Fig. 12b) along with benzoic acid derivatives (24). This 1 3 complex exhibits a hexagonal columnar mesophase between 23 °C and 75 °C. The acrylate moieties on the alkoxyl chains could be photopoly-merized to covalently fix the LC phase. Removal of the supramolecularly bound benzotri(imidazole) core yields a nanoporous polymer film containing hexagonally-ordered channels-opening the door to the potential application of these materials in such areas as separation, nano-composites, and catalysis. 

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