We investigated the relationship between the morphology and viscoelasticity of epoxy/silica hybrid materials manufactured via two different processes: simultaneous formation of epoxy and silica phases and sequential formation of silica phase in the prepared epoxy phase. The glass transition phenomena of the hybrid materials mostly depended on their silica structure. The particular structure did not affect T-g much, while the silica chain structure greatly raised Tg of the hybrid samples. The storage modulus E' depended on the volume fraction of the silica phase, rather than the silica structure. In the glassy state, E' of the hybrid samples slightly decreased when compared with the neat epoxy samples. Lack of chemical reaction between the silica and the epoxy phases could be attributed to this decrease at which the silica structure could have worked as a flaw. In the rubbery state, E' greatly increased with increasing silica content regardless of the silica structure, and this behavior well agreed with that predicted by the Davies model, because the physical interaction worked very well in the rubbery region. (C) 2007 Wiley Periodicals, Inc.