Association of polyacrylic acids with metronidazole

Intermolecular interactions in mixtures of dilute solutions of poly acids with 1-(β-hydroxyethyl)-2-methyl-5-nitroimidazole were studied by viscometry, potentiometry, and IR spectroscopy. The rheological behavior of dilute aqueous solutions of polyacrylic and polymethacrylic acids and of metronidazole at a total concentration of the components of 0.1 wt % was examined. The composition dependences of the specific viscosity show positive deviations from the additivity with a maximum at approximately 50% relative content of the poly acid. In these mixtures, polyelectrolytic complexes stabilized by hydrogen bonds are formed. The strength of the associates increases with an increase in the temperature to 40°C. Hydrophobic groups in macromolecules of the poly acid play a significant role in stabilization of the complexes. In aqueous solutions metronidazole interacts with acrylic, methacrylic, and hydrochloric acids, and in the solid state it forms linear hydrogen-bonded associates.