| Abstract: | Copolymers of acrylamide, 2‐acrylamide‐2‐methylpropanesulfate (AMPS), and hydrophobic monomer N‐arylalkylacrylamide (BAAM) were synthesized by free‐radical micellar copolymerization. The effects of the copolymer, BAAM, AMPS, and NaCl concentrations and the pH value on the apparent viscosity of the copolymers were studied. The solution viscosities increased sharply when the copolymer concentration was higher than the critical associating concentration. The apparent viscosities of aqueous solutions of poly(N‐arylalkylacrylamide‐co‐acrylamide‐co‐2‐acrylamide‐2‐methylpropanesulfate) (PBAMS) increased with increasing BAAM and AMPS concentrations. PBAMS exhibited good salt resistance. With increasing pH, the apparent viscosities first increased and then decreased. Dilute PBAMS solutions exhibited Newtonian behavior, whereas semidilute aqueous and salt solutions exhibited shear‐thickening behavior at a lower shear rate and pseudoplastic behavior at a higher rate. Upon the removal of shear, the aqueous solution viscosities recovered and became even greater than the original viscosity, but the salt solution viscosities could not recover instantaneously. The elastic properties of PBAMS solutions were more dominant than the viscous properties, and this suggested a significant buildup of a network structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 316–321, 2005 |
