The complex formation between polymethacrylic acid (PMAA) and the copolymers of adipic acid (AdA) with poly(ethylene glycol) (PEG) in dilute solution has been studied. The hydrophobic AdA fragments break the continuous cooperative hydrogen bonds between the polymer components in the polycomplex being however the factor that stabilizes the polycomplex (PMAA.AdA/PEG). If the AdA/PEG copolymers are of one and the same chain length the copolymer having more AdA hydrophobic fragments exhibits greater complex forming ability.