Comonomer effects on binding performances and morphology of acrylate-based imprinted polymers

The objective of this study was to investigate the effect of different functional groups of molecularly imprinted polymers (MIPs) on the binding characteristics towards a specific template molecule by examining selectivity and recognition processes. Several non-covalent theophylline imprinted polymers (TIPs) were prepared by using only methacrylic acid (MAA), or MAA and 2-hydroxyethyl methacrylate (HEMA) comonomer, or MAA and acrylamide (ACM) comonomer. In all cases, a high amount of ethylene glycol dimethacrylate (EDMA) as crosslinker existed in the medium. The highest selective theophylline binding of TIPs was found to be 61%, 41% and 40% for MAA/EDMA, MAA/HEMA/EDMA and MAA/ACM/EDMA systems, respectively. The use of a comonomer (ACM or HEMA) reduced the binding performance of the MAA/EDMA polymer matrix, probably due to the monomer-monomer association and morphological differences. Results obtained from the batch binding experiments demonstrated that all of the TIPs have sites that have selective binding ability for theophylline, but not to another structurally similar molecule, caffeine. According to the Langmuir isotherm model, a heterogeneous distribution of binding sites was observed in the polymers. The maximum association constant and binding site density were computed as 2.3 × 102 mM−1 and 8.6 μmol/g, respectively, for copolymer of MAA/EDMA under the examined concentration range.