Transparent and homogeneous polymer hybrids were obtained from a series of random styrene/N,N-dimethylacrylamide copolymers (PSnPAm) and octa(3-hydroxypropyldimethylsiloxy)octasilsesquioxane (Cube-OH) by means of the sol-gel reaction of phenyltrimethoxysilane (PTMOS). The resulting ternary polymer hybrids were prepared via two simultaneous physical interactions [hydrogen-bonding and aromatic (pi-pi) interactions] in one system. Cube-OH and PTMOS were used to form hydrogen-bonding and aromatic (pi-pi) interactions, respectively, with the organic copolymer. When PS90PA10 was used as an organic polymer for the two physical interactions, the transparency was maintained when the weight ratio of Cube-OH to PTMOS was increased to 0.5. However, the polymer hybrids with PS65PA35 produced optically translucent or turbid materials, which indicated the phase separation of the organic polymer and silica gel. The homogeneity of the ternary polymer hybrids was dependent on the balance between the intensity of the hydrogen-bonding interaction and that of the aromatic (pi-pi) interaction. The homogeneity was supported by the results of Fourier transform infrared, differential scanning calorimetry, scanning electron microscopy, and X-ray diffraction, which demonstrated a nanometer-level integration of the organic polymer, Cube-OH, and silica gel. The initial decomposition temperature of the ternary polymer hybrids was more dependent on the amount of PTMOS than on that of Cube-OH. (C) 2003 Wiley Periodicals, Inc.