AbstractThis article presented a novel modification on the melt intercalation. Montmorillonite (MMT) with exothermal enthalpy effect was prepared by the compounding of MMT with AIBN in solution. An exfoliated polystyrene (PS)/MMT nanocomposites could be obtained by the introduction of exothermal MMT via melt mixing, and the comparison with the counterpart indicated the exfoliation of MMT was accelerated by the in situ exothermal enthalpy and nitrogen released during melt intercalation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2230–2236, 2004