Emulsion templating using high internal phase emulsions is an effective route to prepare low density and high porosity macroporous polymers known as polymerized high internal phase emulsions (polyHIPEs). Conventional polyHIPEs, synthesized from surfactant stabilized w/o emulsions have low permeabilities and poor mechanical properties. We present interconnected open macroporous low density nanocomposites produced by polymerizing the continuous phase of emulsion templates, which contained styrene, polyethyleneglycoldimethacrylate, and silylated silica particles. Polyethyleneglycoldimethacrylate and the silylated silica particles acted as crosslinker. The functionalized silica particles were incorporated into the polymer, which resulted in a significant improvement of the mechanical properties of the polyHIPEs without affecting the interconnected and permeable pore structures. The polyHIPEs contained up to 60 wt % silylated silica particles. Young's modulus of the reinforced macroporous polymers increased up to 600% compared with nonreinforced macroporous polymers. The mechanical performance was further increased by increasing the foam density of the macroporous nanocomposites from around 200 to 370 g/cm(3) by raising the organic phase volume of the emulsion templates from 20 to 40 vol %. The macroporous polymers synthesized from less concentrated emulsions also possessed interconnected open porous although less permeable structures. The polyHIPE nanocomposites have a permeability of about 200 mD, whereas the polyMIPE nanocomposites still have permeabilities of around 50 mD. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1979-1989,2010