On the Cause of Controlling Affinity to Small Molecules of Imprinted Polymeric Membranes Prepared by Noncovalent Approach: A Computational and Experimental Investigation

Imprinting technique applied to membrane preparation via phase inversion methods yields membranes with enhanced affinity toward target molecules. In the imprinted membranes prepared by noncovalent approach hydrogen bond and electrostatic interactions can play a crucial role in determining the performance of these membranes. In this work, quantum mechanical calculations and experiments were performed to understand the physical-chemical causes of the affinity increase in imprinted polymeric membranes to 4,4'-methylendianiline (MDA), dissolved in an organic solvent. An ad hoc synthesized copolymer of acrylonitrile and acrylic acid was used to prepare the membranes. The calculated binding energies show that the hydrogen bonds and electrostatic interactions among polymeric chains are comparable to the strength of the same interactions occurring between polymer and MDA. Using this result and correlated experimental data, this work concluded that one of the causes responsible for the increased affinity of the imprinted membranes is the augmented availability of free carboxylic groups in the nanocavities of the membranes. However, along with this reason, the membrane pore sizes must evermore be taken into account. The knowledge acquired in this study helps us to better understand the mechanisms of molecular recognition and hence to optimize the design of new imprinted membranes.