Monitoring the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules: theory and practice

Abstract

The objective of this study was to explore the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules. Here, R-, S- and R/S-1-aminoindanes (TR, TS and TR/S) were used as the model template molecules. Optimization of synthetic protocols facilitated preselection of the most efficient composition for a molecularly imprinted polymer (MIP)—methacrylic acid-co-ethylene glycol dimethacrylate—with satisfactory specificity and an imprinting factor equal to 3. This polymer composition was used further to analyse the effect of configuration of the template on adsorption properties. The results showed preferable adsorption of R-enantiomer, TR in the R-MIP and S-enantiomer, TS in the S-MIP but revealed variations in the binding capacities of TR and TS in the R- and S-cavity (stereoselectivity factor; k = 1.66 to 1.22, respectively). The theoretically analysed binding energies (ΔEB) of both TR and TS in the R-cavity (ΔEB = − 506.14 to − 256.77 kcal mol−1) and S-cavity (ΔEB = − 302.42 to − 347.18 kcal mol−1) were in agreement with empirical data. Morphology and porosity analyses revealed the impact of the template molecule on the pore system of the MIP and control (a non-imprinted polymer), but enantiomers were only found to have a negligible role. Binding characterization revealed that the physisorption-governed adsorption process and Dubinin–Radushkevich model fitted the experimental data best. Finally, terahertz spectroscopy was employed to confirm the similarity between both materials imprinted by each enantiomer.