In this article, a series of hybrid materials consisted of epoxy resin matrix and well-dispersed aminomodified silica (denoted by AMS) nanoparticles were successfully prepared. First of all, the AMS nanoparticles were synthesized by performing the conventional acid-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS), which acts as acceded sol-gel precursor in the presence of 3-aminopropyl trimethoxysilane (APTES), a silane coupling agent molecules. The as-prepared AMS nanoparticles were then characterized by FTIR, C-13-NMR, and Si-29-NMR spectroscopy. Subsequently, a series of hybrid materials were prepared by performing in situ thermal ring-opening polymerization reactions of epoxy resin in the presence of as-prepared AMS nanoparticles and raw silica (RS) particles (i.e., pristine silica). AXIS nanoparticles were found to show better dispersion capability in the polymer matrices than that of RS particles based on the morphological observation of transmission electron microscopy (TEM) study. The better dispersion capability of AMS nanoparticles in hybrid materials was found to lead enhanced thermal, mechanical properties, reduced moisture absorption, and gas permeability based on the measurements of thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and gas permeability analysis (GPA), respectively. (c) 2008 Wiley Periodicals, Inc.