Selectivity control by chemical modification of the recognition sites in two-point binding molecularly imprinted polymer

We demonstrated the possibility of modifying the selectivity of a two-point binding imprinted polymer by chemical modification of the binding sites inside the cavities. We used a thermally reversible bond for the preparation of the monomer-template complex, which allowed us to remove the template easily by means of a simple thermal reaction and to simultaneously introduce various functional groups into the cavity. A phenylmaleimide having an azidocarbonyl group was reacted with diethylstilbestrol (DES, template) to yield a monomer, where the template was linked to two polymerizable maleimido groups via a thermally reversible urethane bond. The polymerization of the monomer was carried out in the presence of ethylene glycol dimethacrylate (EGDMA) by the initiation with 2,2-azobis(isobutyronitrile) (AIBN) at 54 degreesC in DMF. The polymers were refluxed in 1,4-dioxane in the presence of a nucleophile such as water, methanol, or aniline. In this extraction step, the template molecules were removed from the polymer matrix, and simultaneously the isocyanato groups, which were generated by the thermal cleavage of the urethane bond, were converted to amino, urethane, or urea groups through their reaction with water, methanol, or aniline, respectively. The specific recognition ability of the imprinted polymers for the template and its structural analogues was dependent on the space between the two binding points as well as on the nature of the functional group. This method is especially propitious for developing artificial receptors for molecules lacking strongly interactive groups.