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 degrees C, with both the dimethyl sulfoxide 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 N-2 atmospheres up to temperatures > 350 degrees C, and also to water hydrolysis. Based on results from thermal analysis, IR analysis, NMR spectroscopy (C-13 CP MAS, Si-29 CP MAS and Al-27 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model has been proposed, in which every third interlayer surface hydroxy group on the aluminol surface of kaolinite has been replaced by a methoxide group.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.