The preparation of stable composites with well-controlled particle location is one of the challenges in formulating new polymer/nanoparticle mixtures. In this study, cetyltriammonium bromide (CTAB)capped monodisperse Ag nanoparticles were prepared and mixed with an equimass blend of polystyrene (PS) and poly(methyl methaaylate) (PMMA) in solution. The surface of the blend film without nanoparticles showed spherical pits with a size of 4.5 mu m in diameter. The integration of CTAB-capped nanoparticles into the blend film developed surface bumps with a size of 0.4 mu m in diameter. The organophilic Ag nanoparticles were distributed heterogeneously in the immiscible PS-PMMA blend. When the diameter of particle domains reached approximately 20 nm, particles were preferentially located at the interface of the PS and PMMA domains. Larger particle domains with a diameter of 90 nm were found to be in the PMMA-rich phase. Isothermal post-treatment of the PS-PMMA/Ag composite films directs the particle domains into PS domains. Thermodynamic factors that contribute to the observed morphologies are discussed. (C) 2015 Elsevier B.V. All rights reserved.