A polyelectrolyte-bound nonionic surfactant (HO(CH2CH2O)(25)C12H25) (C12E25) system was prepared by copolymerization of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and a methacrylate substituted with HO(CH2CH2O)(25)C12H25 in N,N-dimethylformamide initiated by 2,2＇-azobis-(isobutyronitrile). The contents of the surfactant macromonomer unit (f(DE25)) in the copolymers are in the range 10-30 mol %. Dry samples of these copolymers are soluble in water, polymer-bound surfactants undergoing micellization. The micelle formation studied by fluorescence and quasielastic light scattering (QELS) techniques in 0.1 M NaCl aqueous solutions. Steady-state fluorescence data for pyrene probes solubilized in water in the presence of the copolymers suggest that the polymer-bound surfactants associate in both intra- and interpolymer fashions to form micelles. The interpolymer hydrophobic associations were found to commence to occur at a relatively well-defined polymer concentration (C-p), which can be regarded as an apparent "cmc" for interpolymer micelle formation. Such cmc values are 10-100 times smaller than that for discrete C12E25 molecules, the values increasing with increasing f(DE25). Mean aggregation numbers (N-agg) of the terminal dodecyl groups at an end of the (CH2CH2O)(25) spacer group were estimated by a time-dependent fluorescence method. N-agg values were found to be of the same order of that for the discrete C12E25 micelles although the values for the polymer-bound surfactant micelles are somewhat larger than that for the free micelle. The N-agg values were relatively constant over a significant range of C-p. QELS data indicated bimodal distributions of relaxation times with a fast and a slow relaxation mode. The slow made component is due to polymer aggregates that include a number of micelle units formed by polymer-bound C12E25 groups. On the other hand, the fast mode component may be attributed to either a "unimeric" micelle (a micelle formed by a single polymer chain) or an "oligomeric" micelle (a micelle formed by a small number of polymer chains). Hydrodynamic radii (Rh) for the slow mode component are on the order of 60-170 nm exhibiting a tendency to increase with increasing C-p whereas those for the fast mode are 6-8 nm independent of C-p. R-h for discrete C12E25 micelle was found to be ca. 5 nm under the same conditions. On the basis of the characterization, a hypothetical micelle model was proposed where micelle units formed from polymer-bound C12E25 moieties are bridged by polymer chains yielding a micelle network structure.