Several series of copolymers were prepared from N-substituted acrylamides by free radical polymerization in solution. We have selected a group of monomers with varying degree of hydrophilicity including acrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and N-tert-butylacrylamide. The chemical composition in the final copolymers was found to be very close to the original monomer composition in the feed prior to polymerization. In an effort to elucidate the effect of the chemical composition on the phase separations of the aqueous solutions of the copolymers, the lower critical solution temperatures (LCST) of the copolymers in water were determined by differential scanning calorimetry and optical turbidimetry. In principal, the LCST of the copolymers can be adjusted within the freezing and boiling points of the solutions. The copolymers exhibit systematic changes in their LCSTs as a function of their comonomer composition, for which an empirical equation was established.
Посилання на статтю:
Lower critical solution temperatures of N-substituted acrylamide copolymers in aqueous solutions / H.Y. Liu, X.X. Zhu // Polymer. – 1999. – N 40. – P. 6985–6990.