A novel, well‐defined, amphiphilic graft copolymer was synthesized by the free‐radical copolymerization of acrylic acid and an amphiphilic macromonomer, n‐octylphenyl polyoxyethylene acrylate. This acrylic copolymer was characterized by IR and 1H‐NMR. The number‐average molecular weight was determined by gel permeation chromatography to be 4.37 × 104 (weight‐average molecular weight/number‐average molecular weight = 1.23). The graft copolymer exhibited good solubility in water and high surface activity at much lower concentrations. The molecules of the AA–C8PhEO10Ac copolymer formed polymolecular micelles at 3.0 × 10−4 g/mL. The aggregation of the copolymer was examined in aqueous solution by measurement of the fluorescence of 2‐p‐ toluidinylnaphthalene 6‐sulfonate as a fluorescent probe. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008