Montmorillonite was organically modified with distearyldimethyl-ammonium chloride. This organically modified clay mineral and poly(ethylene oxide), (PEO), were solvent-cast blended with chloroform, and the structure and properties of the resulting blends were investigated. The effects of the clay mineral content on the isothermal crystallization of PEO are discussed. From small and wide angle X-ray scattering measurements of the blends, it was found that the clay mineral forms a remarkable geometrical structure in the blend and induces a preferred orientation of PEO crystallites. The effects of the clay mineral content on dynamic behaviour were also studied.