AbstractThe structure of the aggregates of block copolymers containing poly[(N‐acetylimino)ethylene] as hydrophilic block and poly[(N‐acylimino)ethylene]s as hydrophobic block was studied by size exclusion chromatography, dynamic light scattering, and transmission electron microscopy. The morphology of the aggregates, consisting of spherical and rod‐like micelles, depends on the chemical structure of the block copolymers. The adsorption behavior of human serum albumin (HSA) onto each polymer aggregate was studied by size exclusion chromatography. The maximum amount of HSA bound onto the polymer aggregates depends on the morphology of the polymer aggregates. Adsorption isotherms of HSA for each polymer aggregate are in good agreement with a Langmuir adsorption isotherm. The amount of HSA adsorbed onto the aggregates is not influenced by the fatty acid content in HSA. The electrophoretic mobility of the aggregates without HSA is close to zero, and the negative mobility increases when HSA is incorporated into the aggregates. The experimental results suggest that adsorption of HSA to the aggregates occurs mainly at the surface or at the hydrophilic shell of the polymer aggregates, not at the hydrophobic core of the polymer mic