Abstract: Several temperature-and pH-sensitive poly(methacrylic acid-g-N, N-diethylacrylamide) (P(MAA-g-DEAM))graft copolymerswith different compositionswere synthesized by free-radical copolymerization utilizing macromonomer technique. The phase behaviors of P(MAA-g-DEAM) in dilute aqueous solutions were investigated by UV-Vis transmittance measurements and fluorescence probe technique. Studies demonstrated that the P (MAA-g-DEAM)copolymers had temperature-and pH-sensitivities, the two sensitivities were independent each other. These graft copolymers with different compositions had the approximately identical lower critical solution temperature (LCST), their critical phase transition pH values were dependent on the composition of graft copolymers and increased with increasing mass fraction of PDEAM. The PMAA main chain of P(MAA-g-DEAM) in dilute aqueous solution is an expanded coil conformation when the solution pH is higher than 5.5, and the PMAA main chain of P(MAA-g-DEAM) in dilute aqueous solution is a hyper-coiled conformation when the solution pH is less than 5.5. The unique properties of the graft copolymers may find some uses in the design and synthesis of novel nanocomposite materials.

Key words: Temperature-and pH-sensitivity, Graft copolymer, Phase behavior, Critical phase-transition pH, Lower critical solution temperature