PRESSURE-INDUCED BINDING-SITES IN MOLECULARLY IMPRINTED NETWORK POLYMERS

Molecular imprinting in network polymers under high pressure was studi ed as a means of inducing selective binding sites for molecular recogn ition. Network polymers of methacrylic acid and ethylene glycol dimeth acrylate were prepared in the presence of a template, atrazine or amet ryn, by free radical polymerization at either 1 or 1000 bar in three d ifferent solvents. After washing, they were chromatographically evalua ted for rebinding selectivity. In one case, a significantly stronger r ebinding of the template to the polymer prepared at high pressure than to the polymer prepared at normal pressure was observed. On an ametry n-imprinted polymer prepared at 1 bar using 2-propanol as solvent, the capacity factor for ametryn was 2.3, whereas on a polymer prepared at 1000 bar the capacity factor was 3.2. The capacity factors of atrazin e on these materials were 1.2 and 1.4, respectively. With atrazine as the template, no pressure effect was observed and the capacity factors were, within the experimental error, the same on the high-pressure an d the normal-pressure materials. The polymers were characterized by po rosimetry, swelling measurements, IR, and SEM. These data showed that the high-pressure polymers exhibited a more compact structure with low er pore volume, higher density, and higher swelling compared to the po lymers prepared at normal pressure. The origin of the pressure effect on selectivity was discussed in terms of the monomer-template associat ion tendency and in terms of polymer morphology.