This paper presents a one-step preparation of novel nanocomposites consisting of a polymeric flame retardant (PDEPD) and clay. The clay was exfoliated or intercalated in the PDEPD according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. The PDEPD/clay nanocomposites were light-colored and highly water resistant. The initial decomposition temperature of the nanocomposites was higher than 200 C, meeting the processing temperature of many general polymer materials. The char formation of the nanocomposites was fairly high at 700 C, ranging from 43.3% to 53.5%. When the PDEPD/clay nanocomposites were incorporated into polystyrene (PS) and polyurethane (PU) matrix, the flame retardancy of the composites was evidently improved. The TEM images showed that the clay layers were almost exfoliated in PS matrix and mainly intercalative in PU matrix. The PDEPD/clay nanocomposites can be used as novel halogen-free flame retardant agents in many general polymer materials. (C) 2012 Published by Elsevier B.V.