Synthesis of PEi-g-PA12 with concentration of PEi 2-40 wt % was fulfilled in two different ways, as ring-opening polymerization of LL and transamidation of linear PA12 in the presence of core PEi molecules. Both methods provide almost uniform materials. Obtained samples were characterized using different techniques: solution and melt viscosity, molecular weight and molecular weight distribution of star polymers and PA12 "arms" with different content of cores, as well as melt and glass transition measurements, were fulfilled. For clarification of PEi-g-PA12 structure and mechanism of grafting, bis-(hexamethylen)triamin and tris(2-aminoethyl)amin were used as a model core molecules. Participation of not only the primary but also the secondary and tertiary amino groups in the formation of PEi-g-PA12 polymers (until 2-8 wt %, of PEi content) have been established. At higher content of PEi (8-15 wt %), only primary amino groups of core molecules take part in grafting. (c) 2005 Wiley Periodicals, Inc.