Collect. Czech. Chem. Commun. 1993, 58, 2370-2382

Cloud Point Curves of Aqueous Solutions of Poly(N-ethylmethacrylamide)

Miloslav Bohdanecký, Jiří Horský, Vladimír Petrus, Libuše Mrkvičková and Karel Ulbrich

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic


Aqueous solutions of poly(N-ethylmethacrylamide) have a lower critical solution temperature (LCST). Cloud point curves of five polydisperse samples (Mw . 10-6 = 0.06 to 2.04) in aqueous solutions at concentrations from 0.002 to 0.1 g/ml were obtained. The threshold concentration was found to be almost independent of the molecular weight. The threshold temperature decreases moderately with increasing M and the limiting value for infinite M obtained by the Shultz-Flory method is ΘLPE = 340.5 K. This value is lower by 2.5 K than the temperature ΘLη at which the intrinsic viscosity is proportional to the square root of the molecular weight. The difference cannot be assigned to experimental errors. The entropy-of-dilution parameter is negative (ψ = -2) and much higher than the value obtained from dilute solution properties. The differences in Θ and ψ values are discussed in terms of theory of polymer solutions where a higher-order interaction parameter is included.