Quantum chemical evaluation of the selectivity of polyimide with glycine imprints

Abstract

In this study, the selectivity of molecularly imprinted polymers (MIP) for glycine based on polyimide was evaluated by the quantum chemical modelling. The starting material for the synthesis of MIP was polyamic acid (PAA), which is a copolymer of 1,2,4,5-benzenetetracarboxylic acid with 4,4'-diaminodiphenyl ether. Computer modelling of the structures and the calculation of energies were carried out using the Gaussian 09 program by the DFT method at the B3LYP/6-31G (d, p) level with the basis set superposition error (BSSE) correction.
For the description of the structure of a glycine cluster with water at the molecular level, we performed calculations of the glycine-5H₂O complexes in the gas phase and in water. It was shown that in the gas phase water molecules are located more compactly than in water. The presence of a solvent reduces the energy of H-bonds and "splits" the hydration shell. Prepolymerisation complexes were constructed in the presence of hy-drate-separated pairs for establishment of intermolecular interactions between PAA and glycine. Compared to the hydrated structure of glycine, the presence of PAA units in the nPAA-5H₂O-glycine complexes led to a decrease in the number of H-bonds between the glycine and water. The analysis of bond lengths showed that the addition of the second PAA unit led to a weakening of H-bonds between the template and water. In this case, the number of H-bonds between PAA and water increases. It was shown that the more the number of PAA units interacts with glycine through water, the easier the template was removed from the prepolymerisa-tion complexes and left its imprint in the MIP. For the theoretical evaluation of the selectivity of MIP-glycine, the rebinding energies of the imprint with glycine and other amino acids (alanine, valine) were calculated. It was found that MIP has a better ability to recognise glycine, which was used as a template for the polymer synthesis. The study also theoretically revealed the dependence of the MIP selectivity on the pH of the analysed solutions.
It was shown that, the evaluation of the selectivity of MIP with glycine imprints revealed satisfactory agreement between the experimental results and theoretical calculations was observed