Free radical polymerization phosphonic acid

A similar concept was used in the development of artificial chymotrypsin mimics [54]. The esterase-site was modeled by using the phosphonate template 75 as a stable transition state analogue (Scheme 13.19). The catalytic triad of the active site of chymotrypsin - that is, serine, histidine and aspartic acid (carboxy-late anion) - was mimicked by imidazole, phenolic hydroxy and carboxyl groups, respectively. The catalytically active MIP catalyst 76 was prepared using free radical polymerization, in the presence of the phosphonate template 75, methacrylic acid, ethylene glycol dimethacrylate and AIBN. The template removal conditions had a decisive influence on the efficiency of the polymer-mediated catalysis, and best results were obtained with aqueous Na2CC>3. 

Scheme 2.2 Phosphonic acid-containing methacrylamide monomers used to achieve photopolymerization and free radical polymerization in the case of monomers (3) and (4).

The authors proposed a mechanism for the radical polymerization of VPA based on the analysis of and NMR spectra of the polymer. They assumed that the polymerization occurs via cyclopolymerization of the vinylphosphonic anhydride, which may be present in equilibrium with the free acid in water at the polymerization temperature (Scheme 4.9). The formation of anhydrides of phosphonic acids in water at higher temperature is already known.By intramolecular propagation can be formed the six-membered ring, generating the pattern of head-to-tail addition and formation of a... 

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