NMR and IR study of kaolinite intercalation compounds with benzylalkylammonium chlorides

• IR and 13C CP-MAS NMR methods provided detailed data of the kaolinite derivatives.
• Keying of the salts' methyl groups was confirmed by 13C CP-MAS NMR.
• Conformational changes of long alkyl chains were attested by IR and 13C CP-MAS NMR.
• 27Al and 29Si MAS NMR spectra indicated the undistorted kaolinite layers.

Novel intercalation compounds of kaolinite with selected benzylalkylammonium chlorides, obtained using methoxy-kaolinite as a precursor, were characterized by 13C, 27Al, and 29Si solid-state NMR and infrared (FTIR) spectroscopy. The analyses allowed the confirmation of both the formation and structure of precursors (kaolinite-dimethyl sulfoxide and methoxy-kaolinite), as well as the intercalation compounds. According to the 13C CP-MAS NMR spectra of the derivatives with benzyltrimethylammonium chloride (B1), the methyl groups of the molecules, arranged in a monolayer, were keyed into the ditrigonal holes of the kaolinite tetrahedral sheet. The local environment of internal carbons of benzyltributylammonium chloride (B2) butyl chains was mostly perturbed during intercalation. In turn, the structure of the benzyldimethylhexadecylammonium chloride (B5) after intercalation was changed from the solid-like to liquid-like conformation with an increase of gauche conformers, which was attested both by 13C CP-MAS NMR and FTIR. The 13C CP-MAS NMR analysis confirmed that the methoxyl groups attached to the octahedral surface of methoxy-kaolinite were not affected by intercalation. The 27Al and 29Si MAS NMR did not show any significant distortion of the Al-octahedra and Si-tetrahedra after intercalation of the organic salts. The IR analyses indicated an increased amount of intercalated water with the increase of initial salt concentration.

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