In this article, P(AN/VAC)/clay nanocomposites were prepared by an in situ polymerization and characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry. The results show that the P(AN/VAC)/clay exhibit a multilayered structure. The montmorillonite layers are totally exfoliated and distributed uniformly in the P(AN/VAC) matrix. The dimension stability and heat resistance property of P(AN/VAC)/clay are superior to those of P(AN/VAC) alone. (c) 2006 Wiley Periodicals, Inc.