Molecular imprinting under molecular crowding conditions: an aid to the synthesis of a high-capacity polymeric sorbent for triazine herbicides.

Molecular crowding, an important feature of the molecular environments in biological cells, was applied to the synthesis of antibody-mimic polymers selective for a group of biologically active compounds, the triazine herbicides. Synthesis of these polymers was conducted using molecular imprinting under molecular crowding conditions, whereby atrazine (a template molecule) was complexed with methacrylic acid (a functional monomer) in the presence of a macromolecular crowding agent (either poly(methyl methacrylate) (PMMA) or polystyrene (PS)) followed by cross-linking with ethylene glycol dimethacrylate. After removal of atrazine from the polymer matrix, the retention properties and selectivity of the resultant polymers were assessed by chromatographic tests. The addition of a crowding-inducing agent resulted in polymers with superior retention properties and excellent selectivity for triazine herbicides, as compared to polymers prepared without addition of a crowding-inducing agent. An imprinted polymer prepared in the presence of PS as a crowding agent exhibited a retention factor for atrazine an order of magnitude larger than that of an imprinted polymer prepared in the absence of a crowding agent. NMR results suggest that the crowding agent is capable of promoting hydrogen bond formation between atrazine and methacrylic acid, which could account for the effect of crowding on molecular imprinting.