Chemically modified kaolinite. Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite

The interlayer aluminol surface of kaolinite has been modified by the reaction of methanol, at temperatures between 200 and 270 °C, with both the dimethyl sulfoside intercalate of kaolinite (Kao–DMSO) and the N-methylformamide intercalate of kaolinite (Kao-NMF). The product was a methoxy-functionalized organomineral material, which was resistant to thermal decomposition in both air and N2 atmospheres up to temperatures > 350 °C, and also to water hydrolysis. Based on results from thermal analysis, IR analysis, NMR spectroscopy (13C CP MAS, 29Si CP MAS and 27Al MAS) and elemental analysis, a structural model has been proposed, in which every third interlayer surface hydroxy group on the aluminol surface of kaolinite has been replaced by a methoxide group. The methyl groups which point away from this surface are keyed into the (SiO)6 macro-rings of the adjacent silicate surface, resulting in a non-centrosymmetric two-dimensionally ordered organomineral assembly.