Poly(styrene-co-methyl methacrylate) nanocomposites were synthesized using reverse atom transfer radical polymerization (RATRP) in miniemulsion. Cetyltrimethylammonium bromide (CTAB) as a cationic surfactant applicable at higher temperatures was used for miniemulsion stabilization. Successful RATRP was carried out by using 4,4'-dinonyl-2,2'-bipyridine (dNbPy) as ligand. Monodispersed droplets and particles with sizes in the range of 200 nm were revealed by dynamic light scattering (DLS). Conversion and molecular weight study was carried out using gravimetry and size exclusion chromatography (SEC) respectively. By adding clay content, a decrease in the conversion and molecular weight and an increase in the PDI value of the nanocomposites are observed. Thermal stability of the nanocomposites in comparison with the neat copolymer is revealed by thermogravimetric analysis (TGA). Increased Tg values by adding clay content was also obtained using differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) images of the nanoconposite with 1 wt % of nanoclay loading, display monodispersed spherical particles with sizes in the range of similar to 200 nm. SEM findings are more compiled with dynamic light scattering (DLS) results. Well-dispersed exfoliated clay layers in the polymer matrix of the nanocomposite with 1 wt % nanoclay loading is confirmed by transmission electron microscopy (TEM) images and X-ray diffraction (XRD) data. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012