The structures and thermal properties of a series of nanocomposite poly(ethylene oxide)/Laponite films have been investigated by differential calorimetric and thermal analysis and complemented by microscopy and X-ray diffraction experiments. The crystalline structures of the nanocomposite multilayered films can be tuned by controlling the composition, polymer Mw and the water content. We study the concentration, polymer Mw and humidity dependence of polymer crystallinity in selected nanocomposite multilayered films. Results show that the exact sample preparation and history are important in controlling structure and properties and in developing new materials. Complementary microscopy is used to monitor the structural changes. (c) 2006 Elsevier Ltd. All rights reserved.