A hydrophobically associating copolymer was prepared by free-radical polymerization with acrylamide (AM), acrylic acid (AA), and N-allyloctadec-9-enamide (NAE) as monomers. The structure was characterized by Fourier transform infrared spectroscopy, H-1-NMR, C-13-NMR, and scanning electron microscopy. The rheological experiments indicated that the copolymer possessed superior properties compared with partially hydrolyzed polyacryamide. It was found that an AM/AA/NAE/Tween-80 system could effectively decrease the interfacial tension and reduce the surfactant loss caused by stratum adsorption in polymer-surfactant flooding. (c) 2013 Wiley Periodicals, Inc.