The phosphorus- and nitrogen-containing monomer, acryloxyethyl phenoxy phosphorodiethyl amidate (AEPPA), was synthesized and characterized. Poly(St-co-AEPPA)/alpha-zirconium phosphate (alpha-ZrP) nanocomposites with different amounts of alpha-ZrP were then prepared by in situ radical bulk copolymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the alpha-ZrP layers were exfoliated in the polymer matrix. Improvements in thermal stability and char residues of the copolymer and nanocomposites were observed by thermogravimetric analysis (TGA). The incorporation of AEPPA can reduce the flammability of polystyrene (PS). Moreover, further reductions were observed when alpha-ZrP was added The reduction in flammability was attributed to a lower maximum mass loss rate and more char residues of the nanocomposites involved in thermal degradation. (C) 2010 Elsevier Ltd. All rights reserved.