Effect of clay on mechanical, thermal, moisture absorption, and dielectric properties of polyimide-clay nanocomposites was investigated. Nanocomposites of polyimide (ODA-BSAA) hybridized with two modified clay (PK-802 and PK-805) were synthesized for comparison. The silicate layers in the polymer matrix were intercalated/exfoliated as confirmed by wide-angle X-ray diffraction and transmission electron microscopy. Thermal stability, moisture absorption, and storage modulus for these nanocomposites are improved as hybridized clay increases. Reduced dielectric constants due to the hybridization of layered silicates are observed at frequencies of 1 kHz-1 MHz and temperatures of 35-150 degrees C. The tetrahedrally substituted smectite (PK-805) resulted in higher mechanical strength and dielectric constants than those of octahedrally substituted smectite (PK-802), which could be attributed to their stronger ionic bonding between clay layer and polymer matrix. (c) 2007 Wiley Periodicals, Inc.