Polyhedral oligomeric silsesquioxane-containing hybrids of epoxy resins are prepared via the cocuring reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and brominated epoxy resin (EP). The gel time, dispersion, thermal properties, mechanical properties, water absorption, and dielectric properties of the OAPS/EP composites are studied. The gel time of the 1 wt % OAPS composites is significantly higher compared with that of the epoxy resin control. Wide angle X-ray diffraction and scanning electron microscopy show that, at the molecular level, the appropriate amount of POSS cages was dispersed in the epoxy matrix because the POSS monomer participated in the crosslinking reaction. The thermal and mechanical properties of the composites are enhanced as 1 wt % OAPS was added to the epoxy system. The water absorption of the 1 wt % OAPS composite significantly declines. The dielectric constant of the 1 wt % OAPS composite is 0.5 less than that of the epoxy resin control in the range of 100 Hz40 MHz. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012