Aliphatic polyesters having pendant azide groups were prepared by enzymatic polycondensation in the presence of lipase from Candida antarctica type B (CAL-B). The grafting reaction to the N-3-functional polyester was carried out quantitatively at room temperature using copper-catalyzed azide-alkyne cycloaddition (CuAAC, "click" reaction) with monoalkyne-functional poly(ethylene oxide) (alkyne-PEO, M-n = 750 g/mol). Furthermore, both enzymatic polycondensation and "click" reaction were carried out successfully in sequential one-pot reaction. The graft copolymer was surface-active and self-assembled in water. The graft copolymer had a critical aggregation concentration (cac) of 3 x 10(-2) mu M in water determined by surface tension measurements. Above cac, the graft copolymer formed single chains and aggregates having a hydrodynamic radius of similar to 75 nm. Furthermore, the surface activity of the polymers at the air-water interface was studied by Langmuir trough measurements. The Langmuir isotherm of the graft polymer showed a pseudoplateau resulting from desorption of PEO chains into the subphase upon compression.