Montmorillonite (MON) was solvent-cast blended with poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEG) using water as cosolvent. The structure and properties of the blend films have been investigated. From small-and wide-angle Xray scattering measurements of the blends, the silicate layers of MON are found to be well dispersed individually in the PVA-MON blends, while the silicate layers in PEO-MON blends are found to exist in the form of a large clay tactoid. Furthermore, for both blends, it is found that the silicate layers are parallel to the film surface of the blends, and that preferred orientation of polymer crystallites is induced by the presence of MON. The effects of the MON content on the thermal behavior of the PVA-and PEG-MON blends have been studied with a differential scanning calorimeter. Furthermore, the effects of geometry of the silicate layers on dynamic behavior of the blends have been studied.