Spontaneous change in thermosensitive properties of aqueous solutions of poly(<Emphasis Type="Italic">N,N</Emphasis>-dimethylaminoethyl methacrylate) and its mixtures with sodium dodecyl sulfate

It is shown that the properties of aqueous solutions of poly(N,N-dimethylaminoethyl methacrylate) are unstable over time: the pH value spontaneously decreases, the phase separation temperature grows, and the light scattering ability of dispersions arising above the said temperature weakens. These effects are enhanced after dilution of solutions, become less pronounced with an increase in pH, and disappear when the solutions are isolated from atmosphere (under argon). It is inferred that the lability of the indicated properties is associated with acidification of polymer solutions due to their interaction with air carbon dioxide and the enhancement of protonation of macromolecules. Potentiometric and tensiometric measurements have demonstrated that upon introduction of sodium dodecyl sulfate into solutions of poly(N,N-dimethylaminoethyl methacrylate), the surfactant-polymer interaction slows down owing to a spontaneous increase in the charging of macromolecules in the course of time.