Using a real space implementation of the self-consistent field theory, we calculated the morphology and interactions of spherical nanoparticles with radius R-p that are grafted by polymer chains of N monomers immersed in a chemically identical polymer melt of polymerization index P. The calculation shows that, for big particles (RP >> N(1/2)a, with a the segment size), the interactions and density profiles of the grafted layers are that of brushes at flat interface; While for small particles (R-p << N(1/2)a), the interactions and density profiles are characteristic of star polymers. In the case of intermediate grafted chain lengths, that is, R-p similar to N(1/2)a, we found that the grafting density of the polymers and the radius of the spherical nanoparticles are both important in determining the structure and interactions of the grafted layers. Our findings suggest possible ways to tailor the structure and interactions of the nanoparticles to benefit the fabrication of polymeric nanocomposites. (c) 2006 Wiley Periodicals, Inc.