Phase transitions in the aqueous and aqueous-organic solutions of N-isopropylacrylamide copolymers with vinyl heptadecyl ketone

The copolymers of N-isopropylacrylamide with vinyl heptadecyl ketone with a varying ratio of the comonomer units were synthesized by free-radical poly merization, and the phase transitions of these copolymers in aqueous and aq ueous-organic media were studied. The lower critical solution temperature i n aqueous solution is decreased as the content of vinyl heptadecyl ketone u nits in macromolecules is increased. The presence of inorganic salts in the aqueous medium leads to a reduction in the temperature of phase transition , while in the case of quaternary pyridinium salts, the effect is reversed. The phase transition temperature of copolymer solutions shows an extremum dependence on the composition of the mixed solvent water-tetrahydrofurane ( dioxane, acetone), and its minimum value is observed at the volume fraction of organic component equal to 0.3, 0.45, and 0.5 for tetrahydrofurane, dio xane, and acetone, respectively.