Viscosity behavior and surface and interfacial activities of hydrophobically modified water-soluble acrylamide/N-phenyl acrylamide block copolymers

In this study, the viscosity behavior and surface and interfacial activities of associative water-soluble polymers, which were prepared by an aqueous micellar copolymerization technique from acrylamide and small amounts of N-phenyl acrylamide (1.5 and 5 mol %), were investigated under various conditions, including the polymer concentration, shear rate, temperature, and salinity. The copolymer solutions exhibited increased viscosity due to intermolecular hydrophobic associations, as the solution viscosity of the copolymers increased sharply with increasing polymer concentration, especially above a critical overlap concentration. An almost shear-rate-independent viscosity (Newtonian plateau) was also displayed at high shear rates, and typical non-Newtonian shear-thinning behavior was exhibited at low shear rates and high temperatures. Furthermore, the copolymers exhibited high air-water and oil-water interfacial activities, as the surface and interfacial tensions decreased with increasing polymer concentration and salinity.