Polymer cookery: Influence of polymerization conditions on the performance of molecularly imprinted polymers

A set of polymers has been imprinted with (-)-ephedrine at six different temperatures, ranging from -30 to +80 degreesC. Polymer affinity and specificity were observed to be strongly dependent on the polymerization temperature. The experimental results suggest that the polymer is able to "memorize" the temperature used in the polymerization process in a manner similar to previously documented MIP "memory" effects for the template and polymerization solvent. In a study of the effect of temperature on retention and selectivity in HPLC (using the MIP as a column packing), a clear gradient change in the Van't Hoff plots was observed at 20-30 degreesC. This indicates a transition in binding mechanism from exothermic at higher temperatures to endothermic at lower temperatures. These results, supported by the evidence of template-induced MIP swelling, are interpreted in terms of desolvation and conformational changes in the polymers induced by the interaction with the template.