Fundamental studies of molecularly imprinted polymers

Fundamental research on molecularly imprinted polymers (MIPs) was conducted. Methacrylic acid (MAA)/ethylene dimethacrylate (EDMA) copolymers imprinted with ethyl adenine-9-acetate (EA9A) were used for this purpose. Photoinitiated or thermally initiated free radical polymerization in organic solvents produced these materials. The origins, synthesis, and processing of the imprinted polymers are described. A comprehensive review of the analytical methods used in the imprinting field to determine adsorption isotherms and affinity distributions was conducted. The broad applicability of the Freundlich isotherm to MIPs was demonstrated for the first time in the field. A new model for experimental isotherms of MIPs, the Langmuir-Freundlich isotherm, is suggested to be generally applicable for the characterization of these materials. Equations were derived for the continuous affinity distributions which correspond to the Freundlich and Langmuir-Freundlich isotherms and were easy to use. The derived expressions were based on the homotattic patch approximation (HPA) with a local Langmuir isotherm. It was also determined that continuous affinity distributions could be generated from an unspecified global isotherm via the second-order affinity spectrum method (AS). Following the development of the mathematical foundation, it was shown that continuous affinity distributions could be used as a tool for improving the binding ability of MIPs. Three variables in the imprinting process—temperature, template concentration, and crosslinking percentage—were systematically altered to determine their individual effects on the affinity distribution. Lower temperatures and higher template concentrations resulted in greater capacities and weighted average affinities. Higher crosslinking yielded lower capacities, but greater average affinities. It was discovered during these studies that average affinity and heterogeneity increased together, given an exponentially decaying affinity distribution. Such a result has not been previously reported in the imprinting field. Finally, continuous distributions were employed to demonstrate the viability of site-selective chemical modification (SSCM) of binding sites. Protecting high-affinity sites with EA9A during reactions of MIPs with diazomethane or phenyldiazomethane afforded polymers with improved high-affinity to low-affinity site ratios. It was shown that carboxylic acid groups were esterified in the reaction, drastically reducing their ability to bind EA9A via hydrogen-bonding.