The interaction of individual polyelectrolyte chains with micelles containing a hydrophobic nucleus and chemically bound oppositely charged polyelectrolyte chains was studied. The properties and molecular characteristics of an interpolyelectrolyte complex (IPEC) formed by micelles of polystyrene-block-poly-N-ethyl-4-vinylpyridinium bromide and polymethacrylic acid obtained by simple mixing of their dilute aqueous solutions were determined. The possibility of self-assembling of stable water-soluble colloid nanoparticles with the shape and size determined by the corresponding parameters of the nucleus of the initial block copolymer micelle and with the charge sign depending on the ratio of complexing components was demonstrated.