ABSTRACT: Static light scattering and dynamic light scattering were used to investigate the effect of polyelectrolyte chain length and micelle size on the complex formation between a strong polyelectrolyte, poly(dimethyldiallylammonium chloride) (PDMDAAC), and oppositely charged mixed micelles of Triton X-100 (TX100) and sodium dodecyl sulfate (SDS). Although an increase in the molecular weight of PDMDAAC led to high molar mass of the complex, the degree of binding, defined as the mass ratio of micelle to PDMDAAC in the complex, decreased with increasing PDMDAAC molecular weight. The relation between the molar mass and hydrodynamic size indicated that the complex was compact. With increasing micelle size, the structure of the complex changed from one in which a PDMDAAC molecule binds several micelles to one in which large micelles adsorb one or more low molecular weight PDMDAAC molecule(s). Complexes formed from high molecular weight PDMDAAC fractions and large micelles showed a tendency for coacervation