Hydrophobically modified (HM) associating water-soluble poly(N,N-dimethylacrylamide) (PDMA) polymers were prepared by free-radical copolymerizations of DMA and 2-(N-ethylperfluoro-octanesulfonamido)ethyl acrylate (FOSA). The polymerizations were carried out in deionized water in the presence of ammonium persulfate at 50 degrees C or in bulk in the presence of AIBN at 65 degrees C. The copolymerization kinetics monitored simultaneously by F-19 and H-1 NMR spectroscopy indicates that DMA and FOSA is incorporated at the same relative rates throughout the polymerization. The viscosities of the polymer solutions were measured on a Brookfield viscometer and an Ubbelohde capillary viscometer. A large viscosity enhancement was observed in comparison with PDMA homopolymer solutions. The effects of polymer concentration, shear rate, surfactants, salts, and temperatures on the reduced and Brookfield viscosities were investigated. Interestingly, the aqueous solution of the copolymer prepared in bulk exhibits both hydrophobic interaction and polyelectrolyte effects in the presence of anionic perfluorocarbon surfactant. The resulting polymers were also characterized by size exclusion chromatography and by H-1 and F-19 NMR spectroscopy.