THE MICROENVIRONMENTAL EFFECT IN ION-COMPLEXING INTERPENETRATING POLYMER NETWORKS

The effect of the microenvironment surrounding a ligand within a polym er is probed with metal ions and quantified by the corresponding bindi ng constants. Interpenetrating polymer networks (IPNs) allow for the s ynthesis of well-defined substrate-complexing reagents. Poly(N-vinylim idazole) has been prepared within a polystyrene network and the abilit y of the imidazole ligand to complex Cu(II) and Co(II) ions determined . The microenvironment surrounding the imidazole ligand is varied by s ynthesizing polystyrene/poly(N-vinylimidazole-co-ethyl acrylate) IPNs where imidazole is replaced by increasing levels of weakly coordinatin g carboxylate ester groups. The strength of the imidazole-ion interact ion is sensitive to the polymer microenvironment: as the imidazole/est er ratio decreases along the series 1/0, 0.77/0.23, 0.53/0.47, 0.27/0. 73, and 0/1, the Cu(II) binding constants are 3130, 4134, 8203, 3108, and 0 N-1, respectively, and the Co(II) binding constants are 294, 270 , 86, 129, and 0 N-1.