A study on solution properties of poly(N,N‐diethylacrylamide‐co‐acrylic acid)

Poly(N,N‐diethylacrylamide) (PDEA), poly(acrylic acid) (PAA), and a series of (N,N‐diethylacrylamide‐co‐acrylic acid) (DEA‐AA) random copolymers were synthesized by the method of radical polymerization. The measurement of turbidity showed that the phase behaviors of the brine solutions of the copolymers changed dramatically with the mole fraction of DEA (x) in these copolymers. Copolymers cop6 (x = 0.06) and cop11 (x = 0.11) in which acrylic acid content was higher presented the upper critical solution temperature (UCST) phase behaviors similar to PAA. Copolymer cop27 (x = 0.27) presented the lower critical solution temperature (LCST) behavior similar to PDEA. While copolymer cop18 (x = 0.18) in which acrylic acid content was moderate presented both UCST and LCST behaviors. The solution properties of the polymers were investigated by measurements of viscosity, fluorescence, and pH. It is reasonable to suggest that the sharp change of the phase behavior may be attributed to the interaction between acrylamide group and carboxylic group in the (DEA‐AA) copolymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008