Double-hydrophilic block copolymers containing the charged blocks of poly(acrylic acid) (PAAc) and the neutral blocks of monomethyl ether of poly(ethylene oxide) (MEPEO) are synthesized by a free radical block copolymerization of PAAc with monomethyl ether of poly(ethylene glycol) of various molecular weights (M(vMEPEG) - 1.1.10(3)-5.10(3)). It is revealed that the block copolymerization has a matrix character because non-covalent interactions of propagating PAAc chains with MEPEG. This fact points out the formation of intramolecular polycomplexes in the given diblock copolymers, The MEPEO-b-PAAc copolymers obtained are characterized by (1)H NMR spectroscopy.