Polymorphism in poly(vinylidene fluoride) (PVDF)/clay nanocomposites was studied. Poly(vinylidene fluoride)/clay nanocomposites were prepared with melt intercalation. The samples were characterized with X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The nanocomposite exhibited the 0 form. Thermal annealing performed at 125 and 185'C showed that the 0 form of PVDF was stable. The stability of the P form of PVDF was ascertained from these studies. The 0 form of PVDF in the nanocomposites could be due to crystallization in the constrained phase. (C) 2003 Wiley Periodicals, Inc.