Polymethacrylamide intercalated hectorite clay nanocomposites were synthesized by the in situ free-radical polymerization method. The interlayer cation of hectorite clay was modified with cetyl pyridinium chloride and cetrimide, and their effects on the rate of polymerization of methacrylamide and the structure-property relationships of the resulting polymer nanocomposites were investigated. Fourier transform infrared spectroscopy showed a peak around 550 cm(-1) that was due to the metal oxide stretching of hectorite clay in the polymer nanocomposites. High-resolution transmission electron microscopy determined the size of polymethacrylamide as 300 nm. X-ray diffraction was used for the determination of the intercalated products. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 563-573, 2011