Synthesis of N-vinylformamide and 1-vinyl-(1-methacryloyl)-3,5-dimethylpyrazole copolymers and their extraction ability in relation to histidine in water-salt media

Copolymers of N-vinylformamide (VF) with 1-vinyl-3,5-dimethylpyrazole (VDMP) and 1-methacryloyl-3,5-dimethylpyrazole (MDMP) are synthesized by free radical copolymerization in dioxane. The compositions of copolymers are determined by means of UV-spectroscopy and FTIR, and copolymerization constants r1 and r2 are calculated. N-vinylformamide demonstrates higher reactivity than pyrazole-containing monomers in both cases. Solubility of the synthesized copolymers in water was studied. VF–VDMP copolymers are water soluble at VF content higher than 0.65 molar fractions, and VF–MDMP copolymers—at VF content over 0.8 molar fractions. The formation of complexes between water-soluble copolymers and essential α-amino acid histidine in aqueous solutions is confirmed by UV-spectroscopy, FTIR, dynamic light scattering (DLS), and transition electron microscopy. It is found via DLS that the interactions between the amino acid with copolymer macromolecules lead to conformation changes in macromolecular coils. It is shown that VF–VDMP and VF–MDMP copolymers are effective extragents for histidine. Extraction is carried out at different pH values. The highest extraction degree (98%) is achieved in an acidic medium. © 2017, Springer-Verlag GmbH Germany.