SORPTION OF CARBOXYLIC ACIDS BY MOLECULARLY IMPRINTED POLYMERS

Abstract

Molecularly imprinted polymers were synthesized as selective coatings of piezoelectric sensors for determination of carboxylic acids in the intermediate fractions of rectified ethanol. Molecularly imprinted polymers were obtained by reorganizing and imidizing polyamic acid chains in N,N-dimethylformamide in the presence of a template by the non-covalent imprinting method. The ability of molecularly imprinted polymers to recognize the target templates was evaluated by studying their sorption properties in comparison with non-imprinted polymers using direct conductometry in static mode. The equilibrium time of polyimide and molecularly imprinted polymers for acetic, propionic, butyric acids is in the range of 40 - 80 min. The type of sorption isotherm of acetic acid is characteristic of polymeric materials with micropores. During the sorption of acetic acid at low concentrations, the solvent-ethanol strongly competes with the adsorbed substance due to the close molecular sizes and the presence of group -OH. The type of sorption isotherms of propionic and butyric acids refers to the monomolecular adsorption. The sorption of carboxylic acids by molecularly imprinted polyimide is carried out mainly due to the formation of hydrogen bonds between carboxyl groups of adsorbent and adsorbate. According to the sorption data, the degrees of extraction, distribution coefficients, and imprinting factor values were calculated (IF = 3.0-15.1). It is shown that the molecularly imprinted polymers for carboxylic acids have better sorption ability to acid molecules than their non-imprinted polymers. At the same time, the molecularly imprinted polymer for butyric acid has the highest sorption capacity. Thus, the possibility of using molecularly imprinted polymers for carboxylic acids based on polyimide as selective coatings of piezosensors has been established.