Polystyrene (PS)/montmorillonite nanocomposites were prepared by the free-radical polymerization of styrene-containing dispersed clay in a direct current electric field. The intercalation spacing in the nanocomposites, the dispersion, and the orientation of these composites were investigated. The nanocomposites had higher T, and better thermal stability when compared with the virgin PS. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2723-2727, 2010