Влияние различных факторов на коэффициент поглощения водных растворов сополимеров N -винилпирролидона с 2-метил-5-винилпиридином

The spectrophotometric study of aqueous solutions of three copolymers of N -vinylpyrrolidone and 2-methyl-5-vinylpyridine with different ratios of monomer units has been performed, the concentration dependences of the optical density of copolymer solutions at 269 nm were obtained, and the specific optical absorption coefficients of these solutions were calculated. It is established that, for the studied systems characterized by the LCMT (low critical mixing temperature), an increase in the temperature leads to is a marked increase in the specific absorption coefficient. In a homogeneous field, when the solution pH is decreased from 6.0 to 4.0, the specific absorption coefficient of solutions also increases due to a change in the optical absorption of the pyridine fragments of copolymer as a result of their protonation. The concentration of salt (NaCl), at least up to 4.5 wt. %, produces almost no effect on the specific absorption coefficient of solution. The obtained results can be used as the basis for development of quantitative techniques for determining copolymers of N -vinylpyrrolidone and 2-methyl-5-vinylpyridine in aqueous solutions (including, final dosage forms). The most consistent results can be obtained at temperatures up to the transition temperature and in a weakly basic region (for a copolymer containing 35 % pyridine units, pH = 6.0 – 8.0).