The addition of nanoparticles to polymer systems with an existing phase-separated morphology, such as polymer blends, represents an innovative approach to controlling the microstructure and, hence, the macroscopic properties of the material. During the melt mixing of the constituents, the particles migrate toward specific regions of the material and are driven by more favorable thermodynamic interactions. Kinetic effects related to the high viscosity of the polymer melts, however, may lead to nonequilibrium morphologies. This makes the mixing procedure crucial for controlling the space distribution of the filler and, hence, the microstructure of the blend and its final properties. We focused on this topic by investigating the effect of the sequence of addition of the constituents in blends of polystyrene and polyamide 6 filled with an organoclay prepared by melt compounding. We show that the mixing procedure could bring about alterations in the onset of cocontinuity, which could be exploited to enhance the high-temperature mechanical strength of the blends. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3712-3719, 2011