Intercalation of nitroanilines into kaolinite and second harmonic generation

Kaolinite intercalates ortho- and para-nitroanilines (oNA and pNA) between the layers whereas meta-nitroaniline (mNA) is not intercalated. para-Nitroa niline takes a monolayer arrangement with the long axis inclined to the lay ers of kaolinite. oNA molecules also take a monolayer arrangement though th e orientation is not well ordered. Kaolinite-pNA and -oNA intercalation com pounds exhibit second harmonic generation, which is evaluated quantitativel y by the second-harmonic wave generated with evanescent wave (SHEW) method. This indicates noncentrosymmetric arrangements of pNA and oNA, and such or ientations are induced by the asymmetric environment of the interlayer regi on of kaolinite.