The properties of two poly(N-vinylpyrrolidone) derivatives containing ≈40 wt. % of star-shaped macromolecules with fullerene C₆₀ as a branching point were studied by the methods of electrooptical Kerr effect, dielectric polarization of macromolecules in solutions, and viscometry. It was shown that a polar nanoparticle (fullerene amino adduct) that appears at the center of a polymer molecule after covalent addition of end groups of poly(N-vinylpyrrolidone) to C₆₀ drastically changes electrooptical and dielectric characteristics of the parent polymer. It was demonstrated that the fullerene core appreciably affects the size and molecular density of star-shaped poly(N-vinylpyrrolidone) samples in solution.