In this work, the effects of heat and pressure on intercalated structures of isobutylene-isoprene rubber/clay nanocomposites (IIRCNs) prepared by melt blending were investigated. Not only the local intercalated structures were monitored by wide-angle X-ray diffraction, but also the spatial distributions of intercalated structures were observed by transmission electron microscope. The experimental result reveals that the intercalated structures and their spatial distributions in the matrix are extensively altered by the thermal treatment at atmospheric or higher pressure. The possible microstructural models for untreated and treated IIRCNs were put forward. The observed phenomena were interpreted from the viewpoints of thermodynamics and kinetics theories as well as the feature of rubber. Finally, guidelines were proposed for designing curing system to achieve desired intercalated/exfoliated morphology. (c) 2005 Wiley Periodicals, Inc.