Poly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by in situ photoinitiated activated monomer cationic polymerization. The polymerization of cyclohexene oxide through the interlayer galleries of the clay can provide distribution of the clay layers in the polymer matrix homogenously and results in the formation of PCHO/clay nanocomposites. The exfoliated structures were characterized by X-ray diffraction spectroscopy, thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5328-5335, 2009