Experimental and theoretical study of molecular interactions between 2-vinyl pyridine and acidic pharmaceuticals used as multi-template molecules in molecularly imprinted polymer

Abstract

Molecular interactions between functional monomer and template molecules are regarded as the driving force for the success of a molecularly imprinted polymer. In this study, a multi-template molecularly imprinted polymer (MIP) for ibuprofen, naproxen and diclofenac was synthesized in an oil bath set at 70 °C for 24 hours. 2-vinyl pyridine, ethylene glycol dimethacrylate, toluene and 1,1’-azobis-(cyclohexanecarbonitrile) were used as functional monomer, cross-linker, porogen and radical initiator, respectively. A non-imprinted polymer (NIP) was synthesized using a similar approach with the omission of templates. Monomer-template interactions were examined using Molecular Dynamics and Fourier Transform Infrared Spectroscopy (FTIR). Both molecular dynamics and FT-IR results indicated the formation of the hydrogen bond between the templates and 2-vinyl pyridine. Molecular dynamics further revealed the identity of the hydrogen atoms in the templates involved in interactions with nitrogen atom on the functional monomer in the presence of toluene molecules. Surface area obtained for the MIP using Brunauer, Emmett and Teller method was 282 m2/g, whereas 232 m2/g was obtained for the NIP. This indicated that MIP has more binding sites compared to the NIP. Furthermore, batch adsorption and selectivity experiments were carried out in the presence of gemfibrozil as the competitor. When such experiments were carried out in toluene, the adsorption capacities (mg/g) obtained for naproxen, ibuprofen, diclofenac and gemfibrozil were 14.4, 11.0, 14.0 and 7.5, respectively. These results show that the MIP was more selective to the compounds that were used as template molecules.