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Abstract: Molecularly imprinted polyimide for fatty acids was prepared via the structural reorganization and imidization of polyamic acid chains in mixtures of N,N-dimethylformamide and ethanol in the presence of the template. This paper investigates intermolecular interactions of polymer-template complexes, the stability of which affects recognition ability of molecularly imprinted polymers. The aim of the paper is to elucidate the centers of molecular recognition in polyimide during sorption of fatty acids and to study the influence of solvents on the stability of prepolymerization complexes. Computer modelling of structures and energy calculations were carried out using the B3LYP density functional method in basis set 6-31G (d, p) in the program Gaussian 09. The Tomasi polarizable continuum model (PCM) was used for calculations of solvent effects. It has been established that the oxygen atoms in carbonyl groups C=O of molecularly imprinted polyimide are the centers of molecular recognition. There is a decrease in the energies of intermolecular interaction of fatty acid with the polymer unit during the transition from polyamic acid to polyimide. The interaction energies between polyamic acid and fatty acid templates are almost the same. This also occurs for complexes of polyimide and the templates, which indicates the dominance of H-bonds in interaction of the system. When sorption of fatty acid by polyimide takes place, the vibration of C=O group is shifted to smaller frequencies (from 1805 to 1784 cm-1). In experimental IR spectrum, the peak of the C=O group shows the content of fatty acid template in the polymer. After removal of template, the peak decreases. And when sorption of fatty acid occurs, the peak increases again. The competition between interaction of polyamic acid and fatty acid, and their interactions with solvent reduces the stability of prepolymerization complex. When synthesizing molecularly imprinted polyimide for fatty acids, the ratio of N,N-dimethylformamide and ethanol in solvent mixtures is chosen for the best solubility of the components. We chose the ratio of 3:1 for butyric, palmitic and oleic acids.
Template and target information: palmitic acid, oleic acid, butyric acid, fatty acid
Author keywords: polyamido acid, polyimide, polymers with molecular imprint, hydrogen bond, palmitic acid, oleic acid, butyric acid, Quantum chemistry