All-atom molecular dynamics simulations were used to study the morphology of polymer/inorganic composite particles prepared by heterocoagulation. The results were also compared to those of our previous study of the preparation of TiO2/poly(acrylic acid-co-methyl methacrylate) and Fe3O4/polystyrene composite particles. In the simulation system, polymer or inorganic particles were simulated by surface-charge-modified C-60 or Na atoms. Through a combination of analysis of the radial distribution functions of charged atoms and snapshots of the equilibrated structure, three kinds of particle distributions were observed under different conditions. When the polymer and inorganic particles had opposite surface charges and their sizes were very different, the composite morphology showed a core-shell structure with small particles adsorbed onto the surfaces of large particles. Furthermore, when the polymer and inorganic particles had opposite surface charges bet comparable sizes, the polymer and inorganic particles aggregated domain by domain. Finally, when the polymer and inorganic particles were endowed with the same surface charge, the distribution of these two types of particles was homogeneous, regardless of their size difference. The simulation results Were in agreement with the experimental results. The electrostatic interaction and the size of the particles dominated the final morphology of the composite particles when the heterocoagulation method was used. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2275-2284, 2010