The influence of styrene as a reactive diluent on the morphology of vinylester resin-clay hybrids has been studied. Two mixtures of diglycidylether of bisphenol-A diacrylate as vinyl ester resin and styrene (20 and 40%) were prepared. Various weight ratios of styryl-functional organoclay were added to vinylester resin/styrene mixture, followed by polymerization of the mixture up to 160 degrees C. The morphology of the hybrids studied by X-ray diffraction and Scanning Electron Microscope revealed that the dispersion of organoclay increased with the increase of styrene content. The inclusion of styrene to the system gave ordered intercalated nanocomposites. The surface hardness of the hybrid films decreased with adding a higher content of styrene. Thermogravimetric analysis indicates that clay is effective in promoting char-forming reaction of vinylester resin/styrene clay nanocomposites. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers