Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion-exchanged clays [Na+-saponite (SPT) and Na+-montmorillonite (MMT)] and alkyl ammonium ion-exchanged clays (C-12-MMT and C12OOH-MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion-exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion-exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C12OOH-MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion-exchanged clays have higher tensile strengths than those of organic alkyl-exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl-exchanged clays have initial moduli that are better than those of Na ion-exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. (C) 2003 Wiley Periodicals, Inc.